WO2014096222A2 - Thermotropic polymers - Google Patents

Abstract

Polymer particles having a mean primary particle diameter d50 between 50 nm and 10 pm based on the total weight, containing: A. 10 to 100% by weight of a polymer phase A, obtainable by free-radical copolymerization of an oil-in-water miniemulsion having a monomer mixture as oil phase, containing i) 30 to 99.9% by weight of one or more monoethylenically unsaturated monomers II having at least one C₁₂—C₄₈-n-alkyl side chain, ii) 0 to 60% by weight of one or more monoethylenically unsaturated monomers II having at least one C₁—C₁₁-n-alkyl and/or one C₃—C₄₈-i-alkyl side chain, iii) 0.1 to 20% by weight of one or more monomers III having at least two non-conjugated ethylenic double bonds, iv) 0 to 69.9% by weight of one or more (hetero)aromatic, monoethylenically unsaturated monomers IV, v) 0 to 40% by weight of one or more other monoethylenically unsaturated monomers V; and B. 0 to 90% by weight of a polymer phase B, obtainable by subsequent free-radical graft copolymerization, in the presence of the polymer phase A obtained after stage A), of a monomer mixture containing i) 0 to 100% by weight of one or more monomers VI from the group of the C₁—C₁₀-alkyl (meth)acrylates, ii) 0 to 100% by weight of one or more (hetero)aromatic, monoethylenically unsaturated monomers VII, iii) 0 to 50% by weight of one or more other monoethylenically unsaturated monomers VIII, where the percentages by weight of the monomer mixtures used in the respective stages add up to 100% by weight.

Description

 Thermotropic plastics

 The present invention relates to thermotropic molding compositions and processes for their preparation. In particular, the application relates to polymer particles with temperature-dependent refractive index, processes for their preparation and the use of these polymer particles as additives for the production of thermotropic plastics. Furthermore, the invention relates to methods for producing thermotropic plastics and their use.

 Thermotropic materials reversibly change their scattering behavior for electromagnetic radiation when the temperature changes. Thermotropic materials have high light transmission in a certain temperature range or are transparent, that is they show no or only minimal light scattering. This state is also referred to below as the off mode. Either when exceeding or falling below this temperature range, an increase in light scattering is observed. The resulting cloudy condition will also be referred to as on-mode. Thermotropy is a reversible process: when the initial temperature is reached, thermotropic materials return to their original state. Depending on the direction of the switching process, a distinction can be made between positive (increase in turbidity with increasing temperature) and negative thermotropy (decrease in turbidity with increasing temperature). Positively thermotropic materials are of particular interest since they can be used, for example, in glazing of buildings, greenhouses or solar collectors as shading elements for the temperature-dependent regulation of radiation incidence.

 The scattering of electromagnetic radiation takes place on separate domains, which are located in a suitable matrix material. For scattering to occur, domain and matrix must have different refractive indices. In general, the scattering is particularly intense when a) the refractive index difference between domain and matrix is as large as possible, b) the volume fraction of the scattering domains is high and c) the domains have approximately the size of the wavelength of the electromagnetic radiation. With regard to the use of thermotropic materials as a shading element (for example in building facades), it is not the total scatter but the backscatter that is the decisive factor, since in the turbid state as much energy as possible is to be scattered in the rear half space. Maximum backscatter efficiency is achieved when the diameter of the scatter domains is just below the wavelength of the light. Optimum backscattering properties for solar radiation (AM 1.5 Global) result at diameters of d = 200 to 400 nm (P. M. Nitz, "Optical Modeling and Measurement of Thermotropic Systems", Dissertation, Albert-Ludwigs-Universität Freiburg, 1999). However, this optimum is very broad toward larger diameters, so that even with domains in the size range of about 400 to 2000 nm comparable good backscatter properties can be achieved.

With regard to the switching mechanism, two concepts (A and B) for positively thermotropic materials can be distinguished according to the prior art: In Concept A, the optical switching is based on reversible segregation and mixing processes. Such systems consist of at least two components with different refractive indices. In off mode, the refractive index difference between these components does not come into play as they are homogeneously mixed together at the molecular level. The material then has a mean refractive index and is ideally highly transparent. When a certain temperature - the lower critical solution temperature (LCST) is exceeded - phase separation occurs. Scattering masks are formed which predominantly or completely consist of one of the components. Since the refractive index of the scattering domains differs from that of the surrounding matrix, scattering occurs at the domain / matrix interface and the material appears cloudy. Upon cooling below the LCST, the components mix again and the scattering domains disappear, returning the material to its original transparent state.

 Concept A thermotropic materials suitable for glazing elements are either hydrogels (water / polymer mixtures) or polymer blends (mixtures of at least two polymers). Such LCST systems are widely documented in the patent literature. Examples which may be mentioned of thermotropic hydrogels are: US Pat. No. 5,057,560, US Pat. No. 5,147,923, EP 0 678 534 and EP 0 873 367. Thermotropic polymer blends are described, for example, in EP 0 611 803 and EP 0 181 485.

 Thermotropic LCST systems have many disadvantages:

 • Demixing / mixing processes require high mobility at the molecular level. After several switching cycles, partial macroscopic segregation may occur, resulting in permanent turbidity. A permanent and complete reversibility can not be guaranteed.

• Since even the smallest changes in the composition influence the phase behavior, LCST systems react very sensitively to impurities. For example, thermotropic polymer blends are very sensitive to moisture.

 • Due to the required molecular mobility, LCST systems do not show typical use properties for plastics. They do not work as self-contained, self-supporting systems. LCST systems are therefore used in conjunction with a carrier and a cover layer, which is preferably made of glass or a transparent plastic. The integration of the thermotropic material between two layers is usually associated with a high technological effort. In the case of thermotropic hydrogels, an additional edge bond is necessary to prevent water loss. Extensive tests have shown, however, that a diffusion seal of the edge seal against water for periods of more than ten years is difficult to control.

• Thermotropic hydrogels can not be processed thermoplastically due to the water content. It is difficult to extrude thermotropic polymer blends since the individual polymer components generally have distinctly different viscosities. In addition, the processing temperature is above the switching temperature of the polymer blend. After extrusion, no homogeneous polymer mixture is obtained, with the consequence that the turbidity is irreversible, that is, it remains at temperatures below the switching temperature. For the extrusion production of multilayer films with a thermotropic polymer blend intermediate layer, suitable assistants (for example organic solvents) are added in EP 1 218 467. Thus the segregation temperature Although so far increased that it is above the processing temperature. However, these aids must be removed again without residue in an additional process step, since even the smallest impurities can adversely affect the phase behavior of the thermotropic polymer blend.

 • LCST systems are usually durable under both thermal stress and sunlight. Damage is determined by permanent clouding, a decrease in the switching stroke, an increase in hysteresis and yellowing. Stabilizers, such as radical scavengers and sunscreens, often remain ineffective and can also adversely affect the phase behavior.

 • LCST systems react slowly to temperature changes, as the necessary diffusion processes are slow. In particular, the transition from the dull on mode to the clear off mode can take several hours, sometimes even days.

 In thermotropic materials of Concept B, no segregation / mixing operations are involved. Here, the change in transmission is caused by different temperature dependencies of the refractive indices of the components involved. Concept B thermotropic materials also consist of at least two components: a domain-forming additive and a transparent polymer as a matrix. In the off mode, the refractive indices of the domains and the matrix match as best as possible, so that a high transparency is achieved. As the temperature increases, a significant decrease in the domain refractive index is observed, whereas the refractive index of the matrix remains nearly constant. As a result, the system changes to a light-diffusing, turbid state. In order to achieve a significant, as abrupt change of the refractive index with the temperature, as a domain former (thermotropic additives) preferably materials are used which show a phase transition in the switching temperature.

EP 0 000 868, DE 44 33 090, EP 0 946 443, DE 198 25 984 and EP 1 258 504 use low molecular weight organic substances as thermotropic additives which show a melting transition in the range of the switching temperature. In order for domains to be able to form in the respective transparent polymer matrix, the thermotropic additive in the polymer matrix must be at least partially insoluble. Alkanols, carboxylic acids, their esters and amides as well as comparable classes of compounds are mentioned as suitable low-molecular substance classes. The thermo-tropic additive is incorporated neatly, ie "unprotected". This has a number of disadvantages: The thermotropic additive is generally effective only as a thermotrop within a certain concentration range (eg 2 - 5%). Below this concentration range, it is completely soluble and does not form any domains, ie the additive and matrix are present as a uniform phase. Important material properties of the polymer matrix (for example the adhesion to glass or a comparable support) can be impaired as a result. The domain formation begins only above a certain additive concentration, which can vary greatly depending on the matrix. At high additive concentrations, on the other hand, there is the danger that permanent scattering effects will occur over the entire temperature range. The thermotropic switching property would thus largely be lost. Another disadvantage relates to the expected long-term stability: In the light-scattering On mode, the thermotropic additive is liquid and thus can easily undergo diffusion processes. A loss of the switching effect and permanent scattering effects are the result.

 Various processes are proposed for the production of thermotropic layers with low molecular weight organic substances as a thermotropic additive: EP 0 946 443 first prepares a solvent-containing coating solution which is applied by known coating techniques (such as doctoring, spraying or flooding) Substrate (eg float glass) is applied. Subsequently, the solvent is evaporated off and a thermally induced crosslinking is carried out. Evaporation of the solvent releases vapors which are harmful to health and the environment. Increased investment costs for occupational safety are required. DE 198 25 984 discloses the production of thermotropic laminated glass panes based on UV-curing cast resin formulations. The thermotropic resins are filled into a disc space obtained by bonding two sheets of glass together with a suitable spacer. Irradiation with UV light hardens the thermotropic resin. In a modification of this method, EP 1 258 504 claims a process for producing thermotropic films. After curing, the two carrier discs are removed by removing the spacer again from each other. In this way, a thermotropic film can be isolated. In order for the film to be easily separated, the carrier disk is made, for example, of a material with low adhesion properties (eg PTFE, silicone). In addition, EP 1 258 504 describes a process in which a solvent-free UV-curing formulation is applied to a flat carrier surface with a film casting apparatus. After UV curing under exclusion of air, a thermotropic film results, which can be separated from the carrier layer. In summary, none of the methods mentioned meets the requirements for economic production on a large-scale industrial scale.

In the scientific literature (Solar Energy Materials & Solar Cells, 93, 2009, pp. 1510-1517) a further development is described in which the low molecular weight component is incorporated not in the pure state but in the form of core / shell particles in the polymer matrix. The low-molecular component - a / 7-alkane mixture with a melting point between 30 and 40 ° C - forms the core and is encased in a protective polymer shell. By encapsulation of the low molecular weight component, a powdery material is obtained, which is always present in the range of use temperature as a solid and compared to the unprotected additive can be processed much easier. The polymer shell prevents diffusion processes, so that the long-term stability is significantly improved. The technology for the production of cast resin laminated glass is established, but is not suitable for large-area applications. A transfer of this concept to common thermoplastic processing methods, such. B. film extrusion, is described inter alia in DE 10 2007 061 513.

EP 0 985 709 discloses thermotropic plastic molding compositions in which special copolymers are used as the thermotropic component instead of low molecular substances. The copolymers used are thermodynamically immiscible with the matrix polymer and therefore form domains within the polymer matrix after thermoplastic processing. There the thermotropic component exhibits a higher temperature dependence of the refractive index relative to the matrix reversibly clouds the resulting thermotropic molding compound with temperature increase. Thermotropic component are preferably ethylene-glycidyl methacrylate or ethylene-alkyl (Cl- 4) -Glycidylmethacrylat copolymers (such as Lotader ^® GMA types of Arkema) and methacrylate-butadiene-styrene copolymers (such as Paraloid ^® BTA Types by Rohm & Haas). The transparent polymer matrix is preferably composed of amorphous polyamides or copolyamides (such as Grilamid ^® TR-types of EMS Grivory). By compounding, the two components are forcibly mixed into a thermotropic molding compound. For the further processing into moldings, all common thermoforming processes can be used, such as injection molding, injection blow molding and extrusion. In one embodiment, a transparent polyamide is compounded as a matrix component with an ethylene-glycidyl methacrylate copolymer (Lotader ^® GMA AX 8840) as a domain former and processed by injection molding into sheets (100 x 100 x 4 mm). The thus prepared thermotropic polyamide plates show a nearly continuous decrease in the transmission at 560 nm with increasing temperature (room temperature -> 80 ° C). The degree of clouding in the on mode increases as expected with increasing concentration of the thermotropic additive. A disadvantage is that as the additive concentration increases, the transmission also decreases significantly in the off-mode, so that the effective "switching stroke" (difference in transmission between off and on mode) is low This disadvantageous effect occurs even at relatively low additive concentrations (<10%). ), which indicates an insufficient matching of the refractive indices of the additive and the matrix, so that a high volume fraction of scattering domains, as required for a high scattering intensity in the on mode, and at the same time high transparency in the off mode can not be achieved In the very wide switching range (room temperature -> 80 ° C), these systems are not suitable for applications such as building overheating protection where a tight switching temperature range of approximately 25 - 40 ° C or 30 ° C to 40 ° C is required In addition, the method described does not allow to specifically influence the domain size As a result, it is not possible (for example, with regard to backward shedding).

The object of the present invention was to provide thermotropic molding compositions which overcome at least some of the disadvantages of the prior art.

 According to one aspect of the invention, the object is achieved by the provision of particles which can serve as a thermotropic additive. The particles according to the invention can be obtained by copolymerization of

a. 30 to 95 wt .-% of one or more vinyl monomers having an unbranched alkyl side chain of at least 12 carbon atoms

b. 0.1 to 10% by weight of one or more crosslinkers,

c. From 3 to 70% by weight of one or more vinyl monomers having from 1 to 11 carbon atoms in an aliphatic side chain optionally comprising one or more functional groups,

d. 0 to 50 wt .-% of one or more vinyl monomers having an aromatic side group, which is optionally substituted. Thus, according to the present invention, a particle is produced in which vinyl monomers having a long aliphatic side chain in which the number of C atoms is 12 or more with vinyl monomers whose aliphatic side chain contains 1 to 11 carbon atoms may optionally comprise one or more functional groups , is polymerized. The components used a. are unsubstituted. One or more free radical initiators are required for the polymerization.

 Furthermore, vinyl monomers can be present which comprise aromatic side groups, wherein the aromatic side groups can be substituted.

According to the invention vinyl monomer means compounds of the general formula -CH ₂ = CRiR ₂ . In many cases R ₂ = H and R ₁ optionally comprises the side chain via a functional group.

The person skilled in the art is familiar with various vinyl monomers. Particularly suitable vinyl monomers for the process according to the invention are acrylates. In the abovementioned formula, R _{2 is} then -C (= O) OR ₃ and Ri = H. In methacrylates, R ₂ corresponds to the above-mentioned formula-C (= O) OR ₃ and R 1 represents a methyl group. Further suitable compounds are acrylamides in which R _{2 is} -C (= O) -NHR ₃ ; Vinyl ethers in which R _{2 is} -O-R ₃ and z. Vinyl esters in which R _{2 is} the above formula -O-C (= O) -R ₃ .

R ₃ then corresponds to that in a., C. and d. defined side chain / page group.

The skilled worker is familiar with other vinyl monomers.

For the definition of component a. R _{3 is} an unbranched alkyl group, ie acyclic and saturated. Preferred chain lengths are between 12 and 48 carbon atoms.

 As component b. compounds are used which have at least two groups which can react with the vinyl monomers. Two or more ethylenically unsaturated vinyl monomers are particularly suitable as crosslinker or crosslinker mixture.

For component c. the group R ₃ comprises 1 to 11 C atoms of an aliphatic. These may also be acyclic or cyclic and partially unsaturated. In this case, however, R may comprise several functional groups, for example hydroxy groups, esters, ethers, amides, amines, halogens, carboxy groups and combinations. For example, component c. in the radical R ₂ comprise one or two or three hydroxy groups. R could also include one, two or three ester groups. However, it would also be possible to use a combination of a hydroxy group and a halide. Also, mixtures of various vinyl monomers that satisfy the conditions of c. meet are suitable.

As an optional component, as component d. a vinyl monomer in which R _{3 is} an aromatic side group. Aromatic molecules possess a ring system that comprises delocalized electrons in conjugated double bonds or unoccupied p orbitals or lone pairs. Preferred compounds of this type are phenyl compounds. According to the invention, these may be substituted, preferably with halogens. Preference is given to the use of electron-rich heteroaromatics.

In one embodiment, a further layer grafted onto the particle according to the invention by polymerization of vinyl monomers with 1 to 11 C atoms are obtained in an aliphatic or aromatic side chain, d. H . R ₃ is in this case aliphatic or aromatic with 1 to 11 carbon atoms.

 For grafting a further layer, two or more functional crosslinkers having at least two differently reactive C-C double bonds are used.

 The particles according to the invention exhibit a first-order phase transition in the temperature range from -20 to 150.degree.

 The particles of the invention are preferably prepared with an average particle diameter of 100 to 10,000, or 100 to 2000 nm, preferably 100 to 500 nm. The mean particle diameter d50 is the value at which 50% by weight of all particles are heavier than the specified value and 50% lighter than the specified value. Such d50 values are determined, for example, by laser diffraction.

 It is preferred that the particles have a relatively narrow distribution. Thus, the particle diameter d90 value is preferably at a maximum of three times the d50 value. Thus, for example, if the d50 value is 200 nm, the d90 value is preferably 600 nm or less. Preferably, the ratio of d90 to d50 value is therefore <3, preferably <2.

 The particles of the invention may further contain 0 to 10 wt .-% of inorganic particles. Particularly suitable particles are silicates and oxides of the elements Al, Si, Zr, Hf, Ti, Zn, Pb and their possible mixed oxides.

 The invention also relates to a molding composition comprising a matrix and from 1 to 50% by weight of the particles or particles according to the invention, which at least by the components a. and b. be defined, so:

Particles obtainable by polymerization of

a. 30 to 99.9% by weight of one or more vinyl monomers having an alkyl side chain with at least 12 C atoms,

b. 0.1 to 10% by weight of one or more crosslinkers,

c. 0 to 70 wt .-% of one or more vinyl monomers having 1 to 11 carbon atoms in an aliphatic side chain, which optionally comprises one or more functional groups,

d. 0 to 50 wt .-% of one or more vinyl monomers having an aromatic side group, which is optionally substituted.

 Such a molding compound is then a thermotropic molding compound which can change the light permeability under the effect of heat.

 Between the particles and the matrix material, the difference of the refractive indices is preferably <0.5, or <0.3 or <0.2 or <0.1 or <0.05 or <0.01, based on the translucent Status .

 By choosing the components a. to d. in the particle, the refractive index can be controlled.

Preferably, the matrix material itself is transparent or translucent. In the context of the invention transparency is understood to mean light transmission with simultaneous viewing or image transmission. In contrast to transparency, translucency means transparency without visual or visual transparency. Transparent and translucent molded bodies are defined by a Tvis _n h of 75%, preferably 80%, under the measurement conditions, as given in the examples for the optical characterization, with test specimens analogous to Example 6.

In another embodiment of the invention, the object is achieved by the mono- or biphasic polymer particles according to the invention having an average primary particle diameter between 50 nm and 10 μm, preferably between 100 and 2000 nm, in particular between 200 and 1000 nm or 500 to 1000 nm on her total weight

A) 10 to 100 wt .-% of a polymer phase A, obtainable by free-radical copolymerization of an oil-in-water miniemulsion with a monomer mixture as the oil phase containing

 i) from 30 to 99.9% by weight of one or more monoethylenically unsaturated monomers I having at least one C 12 -C 48 n-alkyl side chain, ii) from 0 to 60% by weight of one or more monomethylenically unsaturated monomers II at least one Cl-Cl in-alkyl and / or one C3-C48-i-alkyl side chain,

 iii) from 0.1 to 20% by weight of one or more monomers III having at least two nonconjugated ethylenic double bonds,

 iv) 0 to 69.9% by weight of one or more (hetero) aromatic, monoethylenically unsaturated monomers IV,

 v) 0 to 40% by weight of one or more other, monoethylenically unsaturated monomers V,

and

B) 0 to 90 wt .-% of a polymer phase B, obtainable by subsequent radical graft copolymerization in the presence of the obtained according to step A) polymer phase A of a monomer mixture containing

 i) 0 to 100% by weight of one or more monomers VI from the group of C 1 -C 10 -alkyl (meth) acrylates,

 ii) 0 to 100% by weight of one or more (hetero) aromatic, monoethylenically unsaturated monomers VII,

 iii) 0 to 50% by weight of one or more other monoethylenically unsaturated monomers VIII,

wherein the weight percent of the monomer mixtures used in the respective stages add up to 100 wt .-%.

 The polymerization preferably takes place without addition of an organic solvent in the organic phases. Such solvents may, for. B. n-alkanes such as 1-octadecane.

 The polymer particles according to the invention preferably have no anchor groups deviating from the spherical arrangement in the surface of the particle core.

The particles according to the invention exhibit a first-order phase transition in the temperature range between -20 and 150.degree. In the context of the present invention, the prefix "Cx-Cy-" (with x or y = 1, 2, 3, etc. and y> x) denotes that the associated alkyl compound, compound class or group consists of x to y carbon atoms can exist. Unbranched acyclic alkyl compounds, compound classes or groups have the prefix "n-", branched acyclic or cyclic prefix "i-". "(Meth) acryl" stands for acrylic or methacrylic compounds, "(hetero) aromatic" for aromatic or heteroaromatic compounds, "(hetero) cyclic" for cyclic or heterocyclic compounds.

 To produce thermotropic plastics, the particles according to the invention are mixed with a suitable transparent or translucent plastic. The particles are ideally present in this plastic homogeneously distributed in the form of separate domains. The plastic forms, possibly in conjunction with other additives, the matrix and is therefore also referred to below as matrix plastic.

Characteristic of the occurrence of light scattering are refractive index differences between domain and matrix. At temperatures below the phase transition (OFF mode), the refractive indices of domain n _D and matrix n _{M are the} best match (n _D = n _M ), so that the thermotropic plastic ideally has the transparency or translucency of the pure matrix plastic. In the temperature range of the phase transition the domain refractive index decreases abruptly (n _D <n _M ), whereby light is scattered at the domain / matrix interface and the transparency or translucency is reduced (ON mode). The largest transmission change shows the thermotropic plastic usually in the temperature range of the phase transition. This temperature range is also referred to below as the switching temperature.

 The polymer phase A of the polymer particles according to the invention is a copolymer whose monomer units are selected from at least two (I, III) or from up to five different groups (I to V) or more. The monomers I are essential for the thermotropic switching behavior. Therefore, in order to build up the polymer phase A, it is necessary to polymerize with at least one monomer I. Polymer phase A is additionally crosslinked with at least one monomer III, so that the polymer particles according to the invention are retained in shape and size in the subsequent processing steps. On the other hand, it depends decisively on the target switching temperature and the properties of the matrix plastic (refractive index in the temperature range of the OFF mode, compatibility with the polymer particles, etc.) whether and to what parts by weight monomers from the other classes II, IV and V are copolymerized.

The polymer phase A of the polymer particles of the invention is from 30 to 99.9 wt .-%, preferably from 50 to 97 wt .-%, in particular 60 to 95 wt .-% or 75 to 85 wt .-% of monomer units with n- Alkyl side chains composed of 12 to 48 carbon atoms (monomers I). In some embodiments, the length of the n-alkyl side chains is in the range of 12 to 16 carbon atoms, in others in the range of 20 to 48 carbon atoms. In some embodiments, two or more different monomers are used together.

The monomers I form free-radical polymerization so-called comb polymers. They consist of a polymer backbone and many C12-C48-n-alkyl side chains attached to it. The side chains are usually an anchor group, z. As an ester group, covalently linked to the main chain. Unlike conventional semicrystalline polymers (eg polyethylene) where the backbone crystallizes, the n-alkyl side chains crystallize here (see NA Plate, VB Shibaev, Comb-Like Polymers, Structure and Properties, Polymer Sci.: Macromolecular Reviews 1974, 8, p. 117-253). The melting / crystallization takes place at a certain phase transition temperature T _m . The phase transition temperature T _m can be determined in a known manner by means of differential scanning calorimetry (DSC). The occurrence of side-chain crystallization requires a minimum chain length, which can vary depending on the flexibility of the main chain. The minimum length is usually about 8 to 11 carbon atoms beyond the anchor group. For side chains above the minimum length, the phase transition temperature T _{m increases} with increasing side chain length. Examples are the known phase transition temperatures of the homopolymers of n-tetradecyl acrylate with T _m = 19.5 ° C and n-docosyl acrylate with T _m = 67.7 ° C called (see KA O'Leary, DR Paul, Physical properties of poly ( n-alkyl acrylate copolymer, Part 1. Crystalline / crystalline combinations, Polymer 2006, 47, p. 1226-1244).

By copolymerization of two or more monomers I with different lengths of side chain, each phase transition temperature within the temperature window defined by the homopolymers can be adjusted via the weight ratio. For copolymers of, for example, two monomers I having different lengths of side chain then applies in general: the higher the proportion of the shorter-chain monomer (or the shorter the chain), the lower the number of crystallizable carbon atoms in the copolymer and the lower the T _m .

The monomers I are preferably selected from the group:

 Ia) the ester of α, β-ethylenically unsaturated C3-C4-carboxylic acids and C12-C48-n-alkanols,

 Ib) the mono- and dialkyl esters of α, β-ethylenically unsaturated C 4 -C 6 -dicarboxylic acids having at least one C 12 -C 48 -n-alkyl side chain as the ester radical and

 Ic) the allyl and vinyl esters of C13-C49-n-alkanecarboxylic acids.

 The skilled worker is aware of further groups of free-radically polymerizable, monoethylenically unsaturated monomers I having at least one C 12 -C 48 n-alkyl side chain.

Preferred monomers I from group Ia) are the (meth) acrylates of n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, n-docosanol and n-octacosanol. In addition to the pure compounds, commercial mixtures of C 12 -C 48 n-alkyl (meth) acrylates with n-alkyl radicals of different lengths (for example SA 1618 from BASF) are also suitable. In some embodiments, no octadecyl acrylate is used.

The monomers I of group Ib) include the dialkyl esters of α, β-ethylenically unsaturated C4-C6 dicarboxylic acids having two identical C12-C48-n-alkyl groups, two different C12-C48-n-alkyl groups, a C12-C48-n Alkyl group and a Cl-Cl in-alkyl or C3-C48-i-alkyl group and the corresponding monoalkyl esters having a C12-C48-n-alkyl group. Preference is given to the dialkyl esters of maleic and itaconic acid with n-dodecanol, n- Tetradecanol, n-hexadecanol, n-octadecanol, n-docosanol and n-octacosanol used.

Preferred monomers I from group Ic) are the vinyl and allyl esters of n-tetradecane, n-hexadecane, n-octadecane, n-docosane and n-octacosanoic acid. Radical polymerizable monomers which have a linear alkyl side chain with fewer than 12 carbon atoms or a branched cyclic or acyclic alkyl side chain with 3 to 48 carbon atoms are particularly suitable for lowering the phase transition temperature T _{m of} a polymer formed essentially from the monomers I (monomers II). The monomers II are copolymerized to from 0 to 60% by weight, preferably from 0 to 40% by weight, in particular from 0 to 20% by weight or from 1 to 60% by weight.

The monomers II are preferably selected from the group IIa) of the esters of α, β-ethylenically unsaturated C3-C4-carboxylic acids and Cl-Cl-alkanols or C3-C48-i-alkanols, IIb) the mono- and diesters of α , .beta.-ethylenically unsaturated C.sub.4-C.sub.6-dicarboxylic acids and C.sub.1-C.sub.1-alkanols and / or C.sub.3-C.sub.48-i-alkanols and IIc) the allyl and vinyl esters of C.sub.2-C.sub.12-n-alkanecarboxylic acids and C.sub.4-C.sub.49-i alkanecarboxylic acids.

 Preferred monomers II from group IIa) are the (meth) acrylates of methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, tert-butanol, n-hexanol, n-octanol, 2-ethylhexanol , n-decanol, isodecanol and isooctadecanol, cyclohexanol, 4-tert-butylcyclohexanol, borneol, isoborneol and 3,3,5-trimethylcyclohexanol and dihydrodicyclopentadienyl (meth) acrylate.

Preferred monomers II from group IIb) are the diesters of maleic and itaconic acid with methanol, ethanol, n-butanol, isobutanol and 2-ethylhexanol. Preferred monomers II from group IIc) are vinyl and allyl acetate and the corresponding propionates, butyrates, valerates, capronates, decanoates and laurates. In some embodiments, no vinyl acetate is used.

 The scattering properties of the thermotropic plastic largely depend on the size of the scattering domains (see comments above). The scattering domain size is defined primarily by the diameter of the polymer phase A of the polymer particles according to the invention. In order to maintain the shape and size of the polymer phase A after processing with the matrix plastic, the polymer phase A is preferably crosslinked. For internal crosslinking, it is possible to use free-radically polymerizable di- or polyfunctional crosslinkers (monomers III). This term refers to monomers having at least two nonconjugated ethylenic double bonds. The monomers III are copolymerized to 0.1 to 20 wt .-%, preferably 0.1 to 10 wt .-% with.

 As di- and polyfunctional monomers III purple) are the (meth) acrylic acid esters of polyhydric alcohols, Illb) the vinyl and allyl ethers of polyhydric alcohols and IIIc) di- or poly-allyl, vinyl or (meth) acryl-substituted (hetero ) cyclic and (hetero) aromatic compounds into consideration.

Suitable di- or polyfunctional monomers III of the group IIIa) are, for example, ethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, di (ethylene glycol) di (meth) acrylate, tri (ethylene glycol) di (meth) acrylate, tetra (ethylene glycol) di (meth ) acrylate, di (propylene glycol) di (meth) acrylate, Tri (propylene glycol) di (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, 2-hydroxy-1,3-di (meth) acryloxypropane, glycerol di (meth) acrylate, glycerol 1,3-diglycerolate di (meth) acrylate, neopentyl glycol di (meth) acrylate, diurethane di (meth) acrylate, trimethylolpropane ethoxylate methyl ether di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethoxylate tri (meth) acrylate (EO grade = 3-20), trimethylolpropane propoxylate tri (meth) acrylate, pentaerythritol tri (meth) acrylate, glycerol propoxylate tri (meth) acrylate, di (trimethylol) propane tetra (meth) acrylate , Pentaerythritol tetra (meth) acrylate, di (pentaerythritol) penta (meth) acrylate and di (pentaerythritol) hexa (meth) acrylate.

Suitable di- or polyfunctional monomers III of group IIIb) are, for example, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, di (ethylene glycol) divinyl ether, bis [4- (vinyloxy) butyl] adipate, Bis [4- (vinyloxy) butyl] succinate, bis [4- (vinyloxy) butyl] isophthalate, bis [4- (vinyloxy) butyl] terephthalate, bis [4- (vinyloxy) butyl] -1,6 hexanediyl biscarbamate, 1,4-cyclohexanedimethanol divinyl ether, tris [4- (vinyloxy) butyl] trimellitate, allyl ether and trimethylolpropane diallyl ether.

 Suitable di- or polyfunctional monomers III of group IIIc) are, for example, divinylbenzene, 2,4,6-triallyloxy-l, 3,5-triazine, 1,3,5-triallyl-1,3,5-triazine-2,4 , 6 (1H, 3H, 5H) -trione, tris [2- (acryloyloxy) ethyl] isocyanurate, 1,3,5-triacryloylhexahydro-1, 3,5-triazine, 2,2'-diallylbisphenol-A, 2 , 2'-diallylbisphenol A diacetate ether, 1,4-phenylenedi (meth) acrylate, bisphenol A ethoxylate di (meth) acrylate (EO grade = 2-30), bisphenol A glycerolate di ( meth) acrylate, bisphenol A-propoxylate glycerolate di (meth) acrylate, bisphenol A di (meth) acrylate and bisphenol F-ethoxylate di (meth) acrylate.

In the temperature range of the OFF mode, a degree of transparency or translucency is sought for the thermotropic plastics, which ideally corresponds to that of the pure matrix plastic. For this purpose, it is necessary in most cases, to match the refractive index of the polymer particles according to the invention to those of the respective matrix plastic. The refractive indices n _D ²⁰ (λ = 589 nm, 20 ° C) suitable transparent or translucent matrix plastics are in the range of 1.35 to 1.65, the majority in the range of 1.49 and 1.59 (see Saechtling plastic paperback, 30th Edition, Carl Hanser Verlag Munich , 2007, Table 8.28, pp. 764-765). Homopolymers and copolymers which are built up from the monomers I and, if appropriate, monomers II, frequently have a lower refractive index at temperatures below the phase transition (OFF mode).

In order to adapt the refractive index of the polymer particles according to the invention in the temperature range of the OFF mode of the matrix plastic, is copolymerized with the (hetero) aromatic monomers IV, wherein the homopolymers of the monomers IV have a refractive index n _D ²⁰ > 1.50, preferably n _D ²⁰ > 1.55 , They are copolymerized with from 0 to 69.9% by weight, preferably from 0 to 50% by weight, in particular from 0 to 30% by weight. In some embodiments, the content of monomers IV is at least 0.1% by weight.

 The monomers IV are preferably selected from the group IVa) of the vinyl (hetero) aromatics and IVb) of the (hetero) aromatic (meth) acrylates.

Suitable monomers IV of group IVa) are, for example, styrene, 4-acetoxystyrene, 2-bromostyrene, 3-bromostyrene, 4-bromostyrene, 4-tert-butoxystyrene, 4-tert-butylstyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene , 2,6-dichlorostyrene, 3,4-dimethoxystyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 4-ethoxy- styrene, 3-methylstyrene, 4-methylstyrene, 4-vinylanisole, 3-vinylbenzyl chloride, 4-vinylbenzyl chloride, 9-vinylanthracene, 4-vinylbiphenyl, 2-vinylnaphthalene, 9-vinylcarbazole, N-vinylphthalimide, 2-vinylpyridine, 4-vinylpyridine and l-vinyl-2-pyrrolidinone.

Suitable monomers IV of group IVb) are, for example, benzyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenyl (meth) acrylate, pentabromobenzyl (meth) acrylate, Pentobromophenyl (meth) acrylate, 2,4,6-tribromophenyl (meth) acrylate, 9H-carbazole-9-ethyl (meth) acrylate, 2-hydroxypropyl-2 - ([meth] acryloyloxy) ethyl phthalate , 1-naphthyl (meth) acrylate and 1-pyrene methyl (meth) acrylate.

 Alternatively or in addition to the monomers IV, it is also possible to use crosslinking monomers III having an aromatic basic structure, such as, for example, B. divinylbenzene, be used for increasing the refractive index.

 To improve the production and processing properties of the polymer particles according to the invention, the monomers V are other monomers which are monoethylenically unsaturated and differ from the monoethylenically unsaturated monomers I, II and IV. They are copolymerized to from 0 to 40% by weight, preferably from 0 to 20% by weight, in particular from 0 to 10% by weight or from 1 to 40% by weight. In some embodiments, the proportion of monomers V is at least 0.1% by weight.

 The monomers V are preferably selected from the group Va) of the α, β-ethylenically unsaturated monocarboxylic and dicarboxylic acids, Vb) of the α, β-ethylenically unsaturated carboxylic acid anhydrides, Vc) of the α, β-ethylenically unsaturated carboxylic acid amides and Vd) of the hydroxy, Alkoxy, carboxy, amino, epoxy, sulfo, silyl and halogen-substituted alkyl (meth) acrylates and heterocyclic (meth) acrylates selected.

 Suitable monomers V of group Va) are, for example, (meth) acrylic acid, maleic acid and itaconic acid.

 Suitable monomers V of group Vb) are, for example, maleic anhydride, itaconic anhydride and crotonic anhydride.

 Suitable monomers V of group Vc) are, for example, N-ethyl, N-isopropyl, N-tert-butyl, N, N-dimethyl, Ν, Ν-diethyl, N-hydroxymethyl, N-hydroxyethyl, N- (3-methoxypropyl) -, N- (butoxymethyl) -, N- (isobutoxymethyl) -, N-phenyl-, N-diphenylmethyl-, N- (triphenylmethyl) - and N- [3- (dimethylamino) propyl] - (meth) acrylamide.

Suitable monomers V of group Vd) are, for example, 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl, 3-hydroxybutyl, 5-hydroxybutyl, hydroxyethyl-caprolactone, 3-chloro-2 Hydroxypropyl, 2-methoxyethyl, 2-ethoxyethyl, 2-butoxyethyl, di (ethylene glycol) methyl ether, di (ethylene glycol) ethyl ether, di (ethylene glycol) -2-ethylhexyl ether, tri (ethylene) glycol) -methylether, ethylene glycol-dicyclopentenyl ether, ethyldiglycol, ethyltriglycol, butyldiglycol, 2-carboxyethyl, 2- (dimethylamino) ethyl, 2- (diethylamino) ethyl, 2- (diisopropylamino) ethyl, 2 (tert-butylamino) ethyl, 3- (dimethylamino) propyl, 2 - [[(butylamino) carbonyl] oxy] ethyl, glycidyl, 2- (methylthio) ethyl, 3- (trimethoxysilyl) propyl, 2- (trimethylsilyloxy) ethyl, 3- [tris (trimethylsiloxy) silyl] propyl, trimethylsilyl, 2-chloroethyl, 2,2,2-trifluoroethyl, tetrahydrofurfuryl and 2-N-morpholinoethyl (meth) acrylate such as 4- (meth) acryloyl-morpholine, mono-2 - ([meth] acryloyloxy) -ethyl succinate and mono-2 - ([meth] acryloyloxy) -ethyl maleate.

 In a preferred embodiment, the monomer phase for the synthesis of the polymer phase A contains

75 to 85% by weight of monomer I

 5 to 10% by weight of monomer II

 3 to 6% by weight of monomer III, 4 to 6% by weight of monomer VI

 3 to 5% by weight of monomer V.

 In other embodiments, the weight ratios of the monomer phase for the preparation of the polymer phase A are

 65 to 75% by weight of monomer I

 15 to 25% by weight of monomer II

 3 to 6% by weight of monomer III

 4 to 6% by weight of monomer V.

In other embodiments, preferred levels of the monomer phase for preparing the polymer phase A are

 • 85 to 92% by weight of monomer I

 3 to 6% by weight of monomer III

 1 to 5% by weight of monomer IV

3 to 6% by weight of monomer V.

 In further embodiments, the content of the monomer phase is at the establishment of the polymer phase A at

 From 85 to 92% by weight of monomer I

3 to 7% by weight of monomer III

4 to 8% by weight of monomer V.

 In further embodiments, preferred compositions of the monomer phase are included in the preparation of the polymer phase A.

 From 85 to 94% by weight of monomer I

3 to 8% by weight of monomer III

3 to 8% by weight of monomer V.

 The stated ingredients of the monomer phase for the preparation of the polymer phase A together amount to 100 wt .-%. In the embodiments mentioned, it is fundamentally possible for further ingredients to be present in the monomer phase. In addition to a polymerization initiator, these can in principle also be additions of other substances. Preferably, the further ingredients are less than 5 wt%, more preferably less than 3 wt%, even more preferably less than 1 wt% or less than 0.5 wt%.

 In some embodiments, the presence of the polymer phase B is necessary.

The preparation of the polymer phase A of the polymer particles according to the invention is carried out by free-radical copolymerization of an oil-in-water miniemulsion.

Polymer particles in the size range of 50 nm to about 1 pm are typically produced by one-stage or multistage oil-in-water emulsion polymerizations (see, for example, BCS Chern, Emulsion polymerization mechanisms and kinetics, Prog 443-486). For a better distinction from the oil in In water miniemulsion polymerization (o / w miniemulsion polymerization), the o / w emulsion polymerization is hereinafter referred to as o / w macroemulsion polymerization. The starting point for the actual polymerization reaction is an o / w macroemulsion in which the monomers to be polymerized form the oil phase. The o / w macroemulsion is usually produced by simple mechanical stirring in the presence of a surfactant. The diameters of the monomer droplets are comparatively large (>> 1 pm) and the size distribution is broad. The monomer droplets are not the main site of polymerization. Rather, they serve as a monomer reservoir, from which the aqueous phase is supplied with the at least partially water-soluble monomer molecules. The surfactant is usually used above the critical micelle concentration (cmc). If this surfactant concentration is exceeded, several surfactant molecules associate to spherical micelles (<10 nm), in the core of which the monomer molecules can be incorporated. The initiator radicals generated in the aqueous phase by water-soluble polymerization initiators can now start the polymerization both in the monomer droplets and in the micelles filled with monomer molecules. Due to the high number of micelles compared to the monomer droplets, the total surface area of the micelles is many times greater, so that a start of polymerization in the micelles is much more likely (micellar nucleation).

 Industrially prepared o / w macroemulsion polymers are, for example, toughening modifiers for poly (meth) acrylate molding compositions. These 2- or 3-phase polymer particles with core-shell or core-shell-shell morphology have an overall diameter in the range of typically 100 to 300 nm (see, for example, EP 1 572 769). For the radical polymerization of extremely hydrophobic monomers, such as the monomers I according to the invention, however, this process is less suitable. For monomer migration from the large monomer droplets through the aqueous phase to the site of polymerization, the water solubility of the monomers I is usually insufficient. A few examples show that the diffusion of hydrophobic monomers by suitable phase transfer agents, such as. As cyclodextrin, can be favored (see, for example, R. J. Leyrer, W. Mächtie, Macromol.Chem Phys., 2000, 201, pp 1235-1243). However, this method is usually not suitable for copolymerizations in which the weight fraction of the hydrophobic monomers in the total monomer mass is 50 wt .-% or more. In addition, relatively large amounts of phase transfer agents are necessary, which causes additional costs for increased use of materials, separation of these additives and possibly recovery.

 In principle, polymer particles constructed from hydrophobic monomers can be synthesized by suspension polymerization. Since radical polymerization by oil-soluble initiators is started here, particle formation takes place almost exclusively in the monomer droplets and not in the aqueous phase. However, in view of the use according to the invention, the particle diameters of suspension polymers are generally substantially too large. Depending on the reaction procedure, polymer particles with diameters between 10 μm and 5 mm are typically obtained (see, for example, Eduardo Vivaldo-Lima et al., An Updated Review on Suspension Polymerization, Ind. Eng. Chem. Res. 1997, 36, p. 939-965).

To build up the polymer phase A of the polymer particles according to the invention, therefore, the miniemulsion technique is used (see, for example, BFJ Schorck, Y. Luo, W. Smulders, JP Russum, A. Butte, K. Fontenot, Adv. Polym. Be. 2005, 175, pp. 129-255). The o / w miniemulsion polymerization differs from the classical o / w macroemulsion polymerization in terms of its performance essentially by two particularities:

a) a homogenization step and

b) optionally by the addition of a costabilizer ("Ultrahydrophob").

In the homogenization step is by the action of high shear forces, for. B. in the form of ultrasound, an o / w miniemulsion generated. This consists of kinetically stable, mostly nano- to submicroscale and narrowly distributed droplets within the water phase. The high o / w miniemulsion stability compared to o / w macroemulsions results from the interaction of a surfactant and a costabilizer. While the surfactant stabilizes the droplets against collision and coalescence, the co-stabilizer prevents so-called Ostwald ripening. This refers to monomer migration from the small to the larger droplets as a result of the high Laplace pressure in the small droplets. The co-stabilizer is dissolved and homogeneously distributed in the droplet phase and has a very low solubility in water, which is why it is often referred to as "ultrahydrophobe." Since the co-stabilizer does not participate in monomer migration through the aqueous phase due to its low solubility in water The formation of a concentration gradient is unfavorable from a thermodynamic point of view Therefore, in the presence of the costabilizer, virtually no Ostwald ripening takes place .. Typical costabilizers are, for example, long-chain alkanes, such as n-hexadecane Polymer phase A usually does not require a costabilizer, since the monomers I generally have a sufficiently low water solubility and thus assume the function of the costabilizer The performance of the process without the addition of a costabi lisators, in particular of 1-octadecane is preferred. In contrast to the o / w macroemulsion polymerization, the particle nucleation takes place in the monomer droplets. This allows a very good control of the particle size, as from almost every droplet a polymer particle is formed. The droplet size and thus the particle size can be adjusted by the type and amount of the surfactant. When using ionic surfactants, the particle diameter is typically from 50 to 500 nm. With nonionic surfactants or by using protective colloids and / or Pickering systems, it is also possible to set larger diameters of up to about 10 μm.

To prepare the polymer particles according to the invention, an o / w macroemulsion is first prepared in a simple manner known per se by mixing the respective monomers necessary for the synthesis of the polymer phase A into a uniform monomer phase and introducing it into an aqueous surfactant solution, for example with mechanical stirring , Depending on the state of matter of the monomer I used or the mixture of two or more monomers I used, it may be advantageous for the monomer phase to be heated beforehand so that a uniform liquid monomer phase results. The temperature is then preferably chosen only so high that the monomer phase is just uniformly liquid. In general, this temperature is in the range or just above the melting temperature of the monomer I used or of the mixture of several monomers I. Advantageously, the aqueous surfactant solution also preheated to this temperature to prevent flocculation of the monomer or I in the combination of both phases. The aqueous surfactant solution may additionally contain buffer substances, such as, for example, sodium hydrogencarbonate, which make the pH of the aqueous phase advantageous with regard to the subsequent free-radical polymerization.

 Suitable surfactants are, in principle, all anionic, cationic and nonionic surfactants which are also suitable for o / w macroemulsion polymerizations. Preferably, anionic and / or nonionic surfactants are used.

Common anionic surfactants are, for example, alkyl sulfates, alkyl sulfonates, alkylaryl sulfonates, alkyl diphenyl oxide disulfonates, alkyl isethionates, alkyl sulfosuccinates, alkyl carboxylates and alkyl phosphates having typically 8 to 18 carbon atoms in the alkyl radical. The counterion is usually an alkali cation (usually Na +) or ammonium (NH4 +).

Common nonionic surfactants are, for example, ethoxylates of fatty alcohols, alkylphenols and fatty acids, each having in each case 4 to 36 carbon atoms in the alkyl radical and an EO degree of 3 to 40.

 The person skilled in further known anionic and nonionic surfactants are known. They are described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, Surfactants, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2012, DOI: 10.1002 / 14356007. a25_747.

 The amount of surfactant is preferably chosen so that the critical micelle formation concentration (cmc) in the aqueous phase of the ultimately resulting o / w miniemulsion is not substantially exceeded. In general, the amount of surfactant is in the range of 0.1 to 5 wt .-% based on the amount of monomers contained in the o / w miniemulsion.

 In order to prevent agglomeration, aggregation, coagulation or flocculation of the primary particles during the polymerization, it may be advantageous to additionally add protective colloids to the aqueous phase. Possible protective colloids are high molecular weight, water-soluble compounds, such as, for example, polyvinyl alcohol, polyvinylpyrrolidone and its copolymers, and also cellulose derivatives, for example methylcellulose and hydroxypropylcellulose. The use of polyvinyl alcohol is less preferred.

 In order to obtain the o / w miniemulsion required according to the invention, the o / w macroemulsion is homogenized by introducing high shear forces. Such high energy input may be produced by emulsifying machines, such as ultrasonic reactors, high pressure homogenizers, rotor-stator systems, static mixers, or combinations thereof. As the energy input increases, the droplet size in the emulsion initially decreases. The amount of energy can be adjusted either via the intensity or the duration of the energy input. For each emulsion of a specific composition, there is a limit to the optimal energy input resulting in a minimum droplet size. Once this minimum droplet size is reached, additional energy introduced merely further reduces the droplet size distribution.

The miniemulsion used according to the invention is an essentially aqueous emulsion stabilized by surface-active substances. on of monomers having a particle size of the emulsified droplets from 10 nm to 600 nm, in particular from 40 nm to 450 nm, preferably from 50 nm to 400 nm.

 The proportion of monomer phase A in the total mass of the o / w miniemulsion is between 5 and 70% by weight, preferably between 20 and 50% by weight, or between 20 and 40% by weight. It is preferred that the proportion of the organic phase is more than 15 or more than 20, or more than 25 wt .-%.

For the synthesis of the polymer phase A, suitable radical radical polymerization initiators are, in principle, all compounds which are capable of initiating a free-radical polymerization. In contrast to o / w macroemulsion polymerization, oil-soluble initiators can be used in addition to water-soluble ones.

 Suitable oil-soluble radical polymerization initiators are the common peroxo and azo compounds, such as, for example, dilauroyl peroxide, dibenzoyl peroxide, tert-amyl peroxypivalate, tert-amyl peroxy-2-ethylhexanoate, 2,2'-azodi (isobutyronitrile) and 1,1'-azobis (cyclohexanecarbonitrile).

 Suitable water-soluble free-radical polymerization initiators are, for example, the ammonium and alkali metal peroxodisulfates, cumene hydroperoxide, tert-butyl hydroperoxide and hydrogen peroxide.

As polymerization initiators, it is also possible to use so-called redox initiator systems. Suitable oxidizing agents for the redox-initiated polymerization are, for example, the abovementioned water-soluble polymerization initiators. Suitable reducing agents are, for example, sodium dithionite, sodium disulfite, sodium hydrogen sulfite and ascorbic acid. Furthermore, the effectiveness of the redox initiator systems can still be improved by adding metal salts, for example iron salts, if appropriate also in conjunction with complexing agents. Other common redox initiator systems are described, for example, in A.S. Sarac, redox polymerization, prog. Polym. Be . 1999, 24, p. 1149-1204.

Depending on the state of matter and solubility behavior of the radical polymerization initiator, it can be supplied in bulk, as a solution, as a suspension or as an emulsion.

 Water-soluble polymerization initiators are preferably added as an aqueous solution only after the homogenization step to the o / w miniemulsion. Thus, the risk of premature polymerization, especially during the energy-intensive homogenization step, can be minimized.

 Oil-soluble polymerization initiators having a sufficiently high decomposition temperature and good solubility in the monomer phase can, as a rule, be added to the monomer phase before the o / w macroemulsion is prepared and completely dissolved therein. Oil-soluble polymerization initiators with low decomposition temperature are preferably added at a later time, then preferably after the homogenization step as a solution, suspension or emulsion.

The addition of the polymerization initiators can be complete, batchwise or continuous. Alternatively, a portion of the polymerization initiator can be added all at once and the remaining portion can be metered in continuously or in portions over a relatively long period of time. In some cases, it may be advantageous to use two or more different oil and / or water-soluble polymerization initiators. These then preferably have different decomposition temperatures and are added at different times before or during the polymerization reaction.

 Usually, from 0.1 to 5% by weight of free-radical polymerization initiator are used, based on the amount of monomer to be polymerized.

 The polymerization temperature depends mainly on the decomposition temperature of the radical polymerization initiators used. Typical polymerization temperatures are between 20 and 100.degree. C., in particular between 50 and 95.degree. Under elevated pressure conditions, the polymerization temperature may be more than 100 ° C. Usually, the polymerization is carried out at atmospheric pressure.

 The reaction times for the formation of the polymer phase A are usually between 1 and 10 hours, usually between 1.5 and 4 hours.

 On the polymer phase A produced by o / w miniemulsion polymerization, in a further synthesis step, a second polymer phase B which is different in its chemical composition from polymer phase A can be grafted on. The synthesis conditions are chosen so that polymer particles with core-shell morphology result. Polymer phase A then forms the inner core and polymer phase B the outer shell.

 Whether an outer polymer phase B is required depends to a certain extent on the compatibility between polymer phase A and matrix plastic. In the case of poor compatibility, the polymer particles according to the invention are only insufficiently dispersed in the matrix art fabric. The particles then often form larger agglomerates or aggregates, whereby the material properties and optical properties of the matrix plastic are impaired.

 With good compatibility between polymer phase A and matrix plastic, preferably no further polymer phase B is grafted onto polymer phase A. This has two main reasons: 1) Through polymer phase B, the weight fraction of polymer phase A decreases in the total weight of the particles. Consequently, in order to obtain a thermotropic plastic with comparable switching properties, the concentration of the polymer particles in the thermotropic plastic must be increased, since only polymer phase A contributes to the thermotropic switching effect. This increases the cost of materials, which usually causes additional costs. In addition, a higher particle concentration can affect the material properties of the matrix plastic. 2) An additional polymer phase can reduce the transparency of the thermotropic plastic in OFF mode. Due to the different chemical composition, the refractive indices of polymer phase A and B and of the matrix also differ at least slightly from one another.

 If a second polymer phase B is grafted onto polymer phase A, the weight fraction of polymer phase B in the total mass of the particles according to the invention is between 5 and 90% by weight, preferably between 10 and 50% by weight, in particular between 15 and 35% by weight. ,

For the grafting of the polymer phase B in the synthesis of the polymer phase A are preferably monomers III with two different reactive, non-conjugate th ethylenic double bonds used. In such graft crosslinking agents, a radically polymerizable double bond (eg, a methacrylic group) reacts at a comparable rate as the monomers I. The second double bond (eg, an allyl group) polymerizes at a significantly lower rate, such that some of these double bonds remain unchanged at the end of the polymerization remain. In this way, a graft crosslinking between two polymer phases is possible.

 Particularly suitable graft-active monomers III are allyl, methallyl and crotyl esters of .alpha.,. Beta.-ethylenically unsaturated carboxylic acids and dicarboxylic acids, preferably allyl (meth) acrylate and diallyl maleate.

 The polymer phase B of the polymer particles according to the invention consists of 0 to 100 wt .-% of one or more monomers VI from the group of C 1 -C 10 alkyl (meth) acrylates, to 0 to 100 wt .-% of one or more (hete- ro) aromatic, monoethylenically unsaturated monomers VII and from 0 to 50% by weight of one or more other monoethylenically unsaturated monomers VIII.

 The monomer selection or the selection of the proportions by weight of the monomers VI to VIII is preferably carried out such that the refractive indices of the polymer phase B in the temperature range of the OFF mode with those of the polymer phase A and the respective matrix plastic match very well. Ideally, polymer phase B and the matrix plastic have the same monomer composition. Polymer phase B and matrix plastic are then to be regarded as one phase, so that only one phase boundary exists between particle core (polymer phase A) and particle shell (polymer phase B). By optimally adapting the refractive indices of both phases, a transparency or translucency can be achieved in the temperature range of the OFF mode that corresponds approximately to that of the pure matrix plastic.

 Preferred monomers VI for the construction of polymer phase B are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-hexyl, n-octyl , 2-ethylhexyl, n-decyl, isodecyl, cyclohexyl, 4-tert-butylcyclohexyl, isobornyl and dihydrodicyclopentadienyl (meth) acrylate.

 Suitable monomers VII are the already mentioned monomers IV.

 Suitable monomers VIII are the monomers V already mentioned.

 In a preferred embodiment for poly (meth) acrylate molding compositions, polymer phase B is synthesized by copolymerization of from 80 to 99.99% by weight of methyl methacrylate and from 0.01 to 20% by weight of a C 1 -C 8 -alkyl acrylate (monomers VI) ,

 To build up the polymer phase B, the necessary monomers are added after completion of the polymerization of polymer phase A to the aqueous dispersion of the polymer phase A. The monomers are preferably added under conditions such that the formation of new particles is avoided and the polymer phase B produced in this polymerization stage accumulates as a shell around the polymer phase A. Preferably, the monomers are added according to their consumption.

Preferably, the monomers necessary for the construction of the polymer phase B are added as o / w macroemulsion to the aqueous dispersion of the polymer phase A. To prepare the o / w macroemulsion, the monomers with an aqueous surfactant solution by z. B. mixed simple mechanical stirring. The aqueous surfactant solution may additionally contain buffer substances in order to make the pH of the aqueous phase advantageous with respect to free-radical polymerization.

Suitable surfactants are, in principle, all surfactants already mentioned. Preferably, identical surfactants are used for both polymerization stages (polymer phase A and polymer phase B).

 The amount of surfactant in the o / w macroemulsion needed to build up the polymer phase B is preferably selected so that the critical micelle formation concentration (cmc) of the surfactant in the aqueous phase containing polymer phase A is not exceeded to minimize the risk of particle formation. In general, the amount of surfactant is in the range of 0.01 to 2 wt .-% based on the amount of monomers contained in the o / w macroemulsion.

To build up the polymer phase B, water-soluble radical polymerization initiators are preferably used. Suitable initiators are the already mentioned water-soluble radical polymerization initiators.

 The addition of the water-soluble radical polymerization initiator may be carried out at once or over a longer period of time during the polymerization of polymer phase B. Alternatively, a part of the polymerization initiator can be added all at once and the remaining part over a longer period of time. Preferably, the water-soluble radical polymerization initiator is metered in continuously with the o / w macroemulsion, either together or via a separate feed.

Usually, 0.01 to 1 wt .-% of radical polymerization initiator based on the amount of monomer to be polymerized used.

 If water-soluble polymerization initiators which are still available in sufficient quantity during the second polymerization stage for the synthesis of the polymer phase B in the first polymerization stage during the synthesis of the polymer phase A can often be dispensed with again by addition of water-soluble polymerization initiators.

 The proportion of monomer phase B in the total mass of the o / w macroemulsion to be metered is between 10 and 80% by weight, preferably between 25 and 70% by weight, in particular between 35 and 60% by weight.

The reaction times for the construction of the polymer phase B after complete addition of the monomers are usually between 0.25 and 8 hours, usually between 0.5 and 4 hours.

Following the actual free-radical polymerization reaction, it is often advantageous to substantially free the resulting particle dispersion of residual monomers and other volatile organic constituents. This can be done for example by steam distillation or by stripping with an inert gas. Furthermore, the residual monomer content can also be reduced by a radical postpolymerization, which can be initiated, for example, by adding the abovementioned redox initiator systems. Further suitable methods are described, for example, in P. H. H . Araujo et al., Techniques for Reducing Residual Monomer Content in Polymers: A Review, Polymer Engineering and Science, July 2002, 42 (7), pp. 1442-1468. Optionally, in the polymerization of the respective polymer phase 0 to 2 wt .-% of a molecular weight regulator can be added. The molecular weight regulator is then part of the respective polymer phase. Molecular weight regulators limit the polymer chain length. In this way, the molecular weight of the polymer phase can be adapted to that of the subsequent phase or of the matrix plastic.

 Suitable molecular weight regulators are, for example, C 1 -C 18 -alkanethiols, such as 2-ethylhexane, 1-dodecane and 1-octadecanethiol.

 After completion of the polymerization, the polymer particles according to the invention are obtained in the form of an aqueous dispersion having a solids content of typically from 20 to 50% by weight. The polymer particles according to the invention can be obtained from the aqueous dispersion, for example by spray drying. However, this method has the disadvantage that the water-soluble polymerization aids are not separated.

In a preferred embodiment of the process, the polymer particles according to the invention are therefore obtained by a sequence of precipitation / coagulation, filtration, washing and drying. Since a direct filtration of the dispersion is usually very time-consuming due to the small primary particle size of the polymer particles according to the invention, the primary particles are precipitated / coagulated prior to filtration. For this purpose, a number of different methods are known. For example, dispersions can be coagulated by the addition of strong electrolytes. In salt coagulation, salts containing polyvalent cations such as Ca 2+, Mg 2+ or Al 3+ are generally used. Furthermore, methods are known which initiate coagulation of polymer dispersions without the addition of salts, for example the application of high shear forces (shear precipitation) or freezing (freeze coagulation).

 In a further preferred process for isolating the polymer particles according to the invention, special extrusion processes are used in which coagulation, dehydration and degassing are carried out with a screw extruder in only one working step (see, for example, DE 2917321). The water phase is separated without leaving behind disturbing residues of water-soluble, non-volatile constituents. The polymer is obtained as a molten strand, which can then be granulated. These processes additionally offer the possibility of mixing the polymer directly with a molding compound as matrix plastic, which eliminates a further working step.

The mean primary particle diameters of the polymer particles according to the invention are chosen to be between 50 nm and 10 μm, preferably between 100 and 2000 nm, particularly preferably between 200 and 1000 nm. Particle diameters in this size range are determined, for example, by laser diffraction. The mean primary particle diameter is the d50 value. d50 then means that 50% by weight of the particles smaller and% by weight of the particles are greater than the stated value. Primary particle means that clumping / adhesion of particles is broken up before size measurement.

The polymer particles according to the invention may furthermore contain 0 to 10% by weight of inorganic nanoparticles. Particularly suitable nanoparticles are silicates and oxides of the elements Al, Si, Zr, Hf, Ti, Zn, Pb and their possible mixed oxides. The particle size of these inorganic nanoparticles is preferably in the Range of 5 to 50 nm. Through this doping, an extended temperature stability is observed in the polymer particles according to the invention.

 The invention also relates to a plastic based on its total weight

A) 1 to 80% by weight of the polymer particles according to the invention,

B) 20 to 99 wt .-% of a matrix consisting of

 i) 50 to 100 wt .-% of at least one transparent or translucent matrix plastic and

 ii) 0 to 50 wt .-% further additives

contains.

 Such a plastic is then a thermotropic plastic or molding material that reversibly changes the light transmittance with temperature change.

 Particularly suitable matrix materials are plastic polymers such as poly (meth) acrylates, polycarbonates, polyolefins, polystyrenes and mixtures thereof. Examples of suitable substances are polyethylene standard homo- and copolymers (eg PE-LD, PE-HD), crosslinked polyethylene derivatives (eg PE-X), ethylene copolymers (PE-ULD, PE-VLD, EVA, EVOH, EBA, EEAK, EMA, EAMA, COC, EIM), polypropylenes (PP), polystyrenes (PS), polystyrene copolymers (eg ABS, SAN), polyvinyl chlorides (PVC), polyvinyl butyrals (PVB), transparent polyamides (PA), polycarbonates (PC) and transparent PC blends, polyethylene terephthalate (PET) and transparent PET blends, polyethylene naphthalate (PEN), polyaryl sulfones (PSU), polyether sulfones (PES), transparent cellulose derivatives (CA, CAB, CAP), and preferably polymethacrylate Homo - and copolymers or impact-modified (PMMA, AMMA, MBS, MABS, PMMI, PMMA-HI).

Suitable matrix plastics are customary transparent or translucent molding compositions, as used for thermoplastic processing. They are selected from the group of polyethylene standard homo- and copolymers (eg PE-LD, PE-HD), the ethylene copolymers (PE-ULD, PE-VLD, EVA, EVOH, EBA, EEAK, EMA , EAMA, COC, EIM), polypropylenes (PP), styrenic polymers (PS, ABS, SAN), polyvinylchlorides (PVC), polyvinyl butyrals (PVB), thermoplastic polyurethanes (TPU), polymethacrylate homo- and copolymers resp impact modifiers (PMMA, AMMA, MBS, MABS, PMMI, PMMA-HI), polyamides (PA), polycarbonates (PC) and PC blends, polyesters of terephthalic acid (PET, PBT) and blends, polyarylsulfones ( PSU), the polyethersulfones (PES) and the cellulose derivatives (CA, CAB, CAP).

Particularly suitable transparent or translucent molding materials from these groups are polymethyl methacrylate (PMMA), impact-modified variants of PMMA (PMMA-HI), methyl methacrylate copolymers (AMMA), polymethacrylmethylimide (PMMI), transparent polyamides (PA) based on aromatic dicarboxylic acids or branched aliphatic or acyclic diamines, transparent polyamides (PA) based on dodecanedioic acid and a cycloaliphatic diamine, polycarbonate (PC) based on bisphenol A, polyethylene terephthalate (PET), polystyrene (PS), polyvinyl butyral (PVB) and thermoplastic polyurethane (TPU). To determine the transparency of the matrix material, reference is made to the measuring method described in the examples.

 In a particularly simple manner, the thermotropic plastic can be prepared by the polymer particles according to the invention with the molding compound as matrix rixkunststoff and optionally other additives by compounding, z. B. in an extruder or kneader, are mixed.

 The resulting thermotropic molding composition can with the usual methods for the formation of thermoplastics, such. As extrusion, calendering, extrusion blow molding, injection molding, injection compression molding, injection blow molding and pressing, to any shaped articles such. B. solid plates, web plates, corrugated sheets, films, rods, tubes or the like.

 Besides thermoplastic molding compositions, other transparent or translucent plastics are also suitable as matrix plastic. These include in particular curable molding compositions and curable casting and laminating resins. In both cases, they are reaction resins which are hardened by the addition of chemical hardeners, by UV or electron beams or by higher temperatures. Suitable reaction resins for the production of thermotropic plastics are, in particular, transparent or translucent formaldehyde resins, unsaturated polyester resins, epoxy resins, silicone resins, diallyl phthalate resins and diallyl diglycol carbonate.

 For the production of thermotropic PMMA, besides the thermoplastic processing with PMMA molding compounds (acrylic glass XT), the so-called casting process (acrylic glass GS) can also be used (DE 639095, see also Ullmann's Encyclopedia of Industrial Chemistry, Polymethacrylates, Wiley-VCH Verlag GmbH & Co KGaA, Weinheim, 2013, DOI: 10.1002 / 14356007, a21_473.pub2). The casting process is particularly important when products of high optical quality, mirror-like surface and high thickness are required. As a precursor for thermotropic acrylic glass GS is preferably a mixture of PMMA, methyl methacrylate (MMA), the polymer particles of the invention, a thermal polymerization initiator and optionally other additives such as (crosslinking) comonomers, stabilizers, etc. used. The polymerization typically takes place in a sealed flat chamber, which consists of two glass plates with a perfect surface and a spacer. For polymerization, the filled flat chamber is heated in a horizontal or vertical position for several hours at a temperature-adjusted temperature program in the range of 20 to 60 ° C. The final polymerization takes place at temperatures of 110 to 130 ° C. Alternatively, thermotropic acrylic can also be made by a continuous casting process such as the double belt process (US 3,376,371).

In principle, the thermotropic molding composition may contain further ingredients, for example lubricants, antiblocking agents, release agents, stabilizers (antioxidants, light stabilizers, heat protectants), antistatic agents, flame retardants, colorants, impact modifiers, plasticizers, adhesion promoters, fillers, reinforcing agents, blowing agents, etc., and mixtures thereof.

In a particularly simple manner, the molding composition can be prepared in which the particles of the invention with the matrix by compounding z. B. in an extruder or kneader. The thermotropic plastics according to the invention can of course also be used for the production of composite materials. For this purpose, the thermotropic plastic is bonded to other materials, such as glass, plastic, wood, metal and the like, so that composite materials, such as multilayer films, laminated glasses, with a thermotropic adhesive film or a thermotropic varnish coated glasses are obtained. Depending on the matrix plastic, the common methods can be used for such. As coextrusion, multi-component injection molding, bonding, laminating, pouring, spraying, knife coating, flooding and the like.

The molding composition according to the invention can then be used for the production of end products, for example by extrusion or injection molding, in order to obtain shaped articles such as solid plates, web plates, corrugated sheets, films, pipes or the like.

 These moldings obtainable therefrom are suitable, for example, as overheating and glare protection in conservatories, in greenhouses, in carports or even in building glazing.

 The thermotropic plastics and the thermotropic molded articles or plastic parts produced therefrom are suitable, for example, for glazing of buildings, vehicles, conservatories, greenhouses and greenhouses; for glass facades, glass facade elements and curtain walls; for solar control glass and light directing solar control glass; for insulating glass, heat-insulating glass and insulating panels; for laminated glass, safety and sound insulation composite glass; for carports, balcony glazing,

Patio roofing, glasshouses, swimming pool halls and roofs; for roof, overhead and skylight glazing; for industrial glazing; for lighting components, skylights, rooflights and barrel vaults; for profiled glass, hollow panes and panels; for transparent insulation; as covers for solar collectors and photovoltaic modules; for sunscreen films and varnishes; for agricultural and greenhouse films; as a laminating film for example laminated glass; for interior glazings, partition walls, room dividers, shower cubicles, glass doors and sliding glass doors; for decorative glass; for luminaire covers, lampshades, reflectors and light guides; for optical lenses and spectacle lenses or their coatings; for illuminated advertising and neon signs; for traffic and information signs and for packaging.

 FIG. 1 shows a scanning electron micrograph of the coagulated dry polymer from Example 1. The average primary particle diameter d50 of the polymer is in the range from 100 to 400 nm.

 FIG. 2 shows two measuring arrangements which were used for optical sample characterization.

 FIG. 3 shows the spectra of normal-hemispheric transmission using Example 9.

FIG. 4 shows the transmission values of the normal-normal, visible transmission (Tvis _nn ) versus temperature, which are calculated from the transmission spectra. The invention is explained in more detail by the following examples. Example 1 - Preparation of the Polvmer Particles According to the Invention

 For example 1, polymer particles according to the invention were prepared which can be used as a thermotropic additive for poly (methyl methacrylate) (PMMA) as matrix plastic. They are suitable both for thermoplastic processing with commercial PMMA molding compounds (acrylic glass XT, examples 6 and 7) and for the production of PMMA castings (acrylic glass GS, examples 8 and 9). The two-phase polymer particles of the invention consist of the polymer phases A and B in a weight ratio of A / B = 75/25 wt .-% (based on the amounts of monomers used). Polymer particles of the invention, which consist only of a polymer phase A, are usually not suitable for thermoplastic processing with PM-MA molding compositions. Due to the usually insufficient compatibility of the polymer phase A with PMMA molding compounds, corresponding moldings often show permanent turbidity, inhomogeneities and numerous particle agglomerates as a damage pattern.

The monomer composition of both polymer phases is given in Tables 1 and 2. The composition of polymer phase A was chosen so that the associated thermotropic PMMA moldings or cast bodies reversibly change their light transmittance mainly in the temperature range of 30 to 40 ° C. Quite generally applies that for a switching temperature of 30 to 40 ° C only those monomers I or mixtures of two or more monomers I come into consideration whose homo- or copolymers have a phase transition temperature T _m above the switching temperature, as by copolymerization with further Monomers from groups II to V of T _{m is} lowered. For polymer phase A, therefore, ODA was selected as monomer I. The phase transition temperature of the homopolymer p (ODA) is T _m = 50 ° C (see KA O'Leary, DR Paul, Physical properties of poly (n-alkyl acrylate) copolymer, Part 1. Crystalline / crystalline combinations, Polymer 2006, 47 , P. 1226-1244) approx. 10 to 20 K above the required for a switching temperature of 30 to 40 ° C phase transition temperature. The

Phase transition temperature of polymer phase A is therefore reduced by copolymerization with BA (monomer II). It should be noted that the other monomers III to V contribute to the lowering of T _m . For the graft crosslinking of both polymer phases A and B, ALMA (monomer III) was incorporated by copolymerization. In order to obtain PMMA cast or PMMA castings with high transparency in the temperature range of the OFF mode, the refractive index of the polymer phase A was determined by copolymerization with styrene (monomer IV) on the PMMA matrix (n _D ²⁰ = 1.49). As the fifth component of the polymer phase A, HEMA (monomer V) was incorporated by copolymerization. As a result, the production and processing properties of the polymer particles according to the invention could be improved.

For polymer phase B, a composition was chosen which typically corresponds to that of commercial PMMA molding compositions. On the one hand, this improves the compatibility of the particles according to the invention with the PMMA matrix; on the other hand, such an optimal match of the refractive indices of polymer phase B and Matrixkunstoff can be achieved, which significantly improves the transparency in the OFF mode. For the production of commercial PM-MA molding compositions, in addition to MMA as main monomer, usually small amounts of acrylates are used as comonomers (for example EA), which are the Give molding compound easy processability and a higher thermal stability.

 starting materials

 Table 1: Monomer phase A for the construction of the polymer phase A.

Substance Mass [g] Percentage [wt / ο] ¹ Monomer ²

 ODA 48.00 80.0 l

 BA 4,20 7,0 II

 ALMA 2,40 4,0 III

 Styrene 3.00 5.0 IV

 HEMA 2.40 4.0V

1: Relative to monomer phase A.

 2: According to the classification of the invention.

 For the radical polymerization of the monomer phase A, 0.60 g of LPO was used as the oil-soluble polymerization initiator.

The associated aqueous phase A is composed of 0.30 g SDS, 0.075 g NaHC0 ₃ and 140 g ultrapure water.

 Table 2: Monomer Phase B for Construction of Polymer Phase B.

Substance Mass [g] Percentage [wt / ο] ¹ Monomer ²

 M MA 19,20 96 VI

 EA OJiO 4 VI

 1: Relative to monomer phase B.

 2: According to the classification of the invention.

 The associated aqueous phase B is composed of 0.020 g SDS, 0.010 g NaHCOs, 0.020 g NaPDS and 20 g ultrapure water.

 Used devices

 Ultrasonic Homogenization: HIELSCHER ultrasonic reactor UP200S with sonotrode S14 and the settings Amplitude 100% and Cycle 1.

 Metering pump: HEIDOLPH PD 5101 pump drive, SP QUICK D 1.6 pump head, TYGON 2001 hose 0.8 / 1.6, metering at level 10.

 Vacuum filtration: filter MACH ERY-NAGEL MN 640 W (medium speed, 150 mm diameter), plastic parts (150 mm diameter), 1000 ml suction bottle, diaphragm pump.

 execution

A tempered at 35 ° C, aqueous phase A was submitted. Monomer I was completely melted in a convection oven at 60 ° C. The monomers II to V were preheated in a water bath (35 ° C) and combined with the liquid monomer I with magnetic stirring. The resulting monomer phase A was heated for a further 15 minutes with continuous stirring at 35 ° C. Immediately prior to the combination of monomer phase A and aqueous phase A, the oil-soluble initiator was added to monomer phase A and completely dissolved with magnetic stirring. The combined phases were predispersed at 35 ° C. for 10 minutes by vigorous stirring with a magnetic stirrer to give an o / w macroemulsion. Subsequently, the o / w macroemulsion was homogenized for 30 minutes with ultrasound to an o / w miniemulsion. During the ultrasonic treatment was cooled with a water bath (25 ° C) and the Internal temperature controlled. In addition, the emulsion was stirred with a magnetic stirrer to ensure a substantially uniform temperature distribution. During the ultrasonic treatment, the internal temperature was in the range of 30 to 45 ° C. After sonication, the o / w mini-emulsion was transferred to a polymerization vessel preheated to 35 ° C. The polymerization vessel used was a 500 ml three-necked flask with reflux condenser, protective gas feed and KPG stirrer. The RPM of the KPG stirrer was set to 300 rpm using an electronic stirrer. To heat the polymerization, a temperature-controlled oil bath was used with Heizrührplatte. For a uniform temperature distribution in the oil bath was stirred magnetically. The o / w miniemulsion was degassed at 35 ° C oil bath temperature and stirring for 15 min in inert gas (argon). The protective gas flow was reduced and the miniemulsion heated to 85 ° C. The mixture was then polymerized for a further 120 minutes at 85 ° C. and constant speed. During the two-hour polymerization time of polymer phase A, the o / w macrophase emulsion for polymer phase B was prepared. For this purpose, the monomer phase B was combined with the aqueous phase B and stirred vigorously with a magnetic stirrer for 30 min. The resulting o / w macroemulsion was added dropwise at 85 ° C. with a metering pump at the end of the two-hour polymerization time of polymer phase A over a period of 45 minutes. After complete addition was stirred for a further 120 min at 85 ° C and constant speed. The oil bath was then removed and the particle dispersion coagulated. For this purpose, the still warm dispersion was transferred to a beaker and mixed with vigorous stirring with a magnetic stirrer with 150 ml_ of a 0.5 wt .-% strength magnesium sulfate solution. The coagulum was filtered under vacuum conditions. The remaining filter residue was washed five more times with 250 ml of water to remove all water-soluble polymerization aids as completely as possible. The moist polymer was dried to constant mass under the hood. There was obtained 73.4 g of a colorless solid.

 particle analysis

 The dry polymer of Example 1 was characterized by differential scanning calorimetry on a PERKIN ELMER DSC 4000. In the temperature range of -20 to 120 ° C and at a heating or cooling rate of 10 K / min, two heating curves and one cooling curve were recorded (sequence: heating curve 1, cooling curve 1, heating curve 2). For the evaluation, cooling curve 1 and heating curve 2 were used. A 1st order phase transition is found. Cooling curve 1: onset temperature = 34.4 ° C, peak temperature = 30.3 ° C, delta H = -39.2 J / g; Heating curve 2: onset temperature = 30.7 ° C, peak temperature = 39.0 ° C, delta H = 39.4 J / g.

FIG. 1 shows a scanning electron micrograph of the coagulated dry polymer from Example 1. The average primary particle diameter d50 of the polymer is in the range from 100 to 400 nm. In the following Examples 2 to 5, the production of further inventive polymer particles with different phase transition temperature is documented.

 Example 2 - Production of the Polvmer Particles According to the Invention

starting materials

 Table 3: Monomer phase A for the construction of the polymer phase A.

Substance Mass [g] Percentage [weight / ο] ¹ monomer ²

 DCA 42.00 70.0 I

 BA 12,60 21,0 II

 ALMA 2,40 4,0 III

HEMA 3.00 5 ₁ 0 V_

 1: Relative to monomer phase A.

 2: According to the classification of the invention.

 For the radical polymerization of the monomer phase A, 0.30 g of AIBN was used as the oil-soluble polymerization initiator.

The associated aqueous phase A is composed of 0.30 g SDS, 0.075 g NaHC0 ₃ and 140 g ultrapure water.

 Table 4: Monomer Phase B for Construction of Polymer Phase B.

Substance Mass [g] Percentage [weight / ο] ¹ monomer ²

 M MA 19,00 95 VI

 EA MX) 5 VI

 1: Relative to monomer phase B.

2: According to the classification of the invention.

The associated aqueous phase B is composed of 0.020 g SDS, 0.010 g NaHC0 ₃ , 0.020 g NaPDS and 20 g ultrapure water.

 execution

 The procedure was carried out analogously to Example 1 with the following changes:

Monomer I was completely melted in a convection oven at 80 ° C.

 The aqueous phase A, the monomer phase A and the prepared from both phases o / w macroemulsion were heated at 45 ° C. During the sonication, the emulsion was cooled with a water bath (35 ° C). The internal temperature was in the range of 40 to 55 ° C. After sonication, the o / w miniemulsion was transferred to a 45 ° C preheated polymerization vessel.

 The polymerization initiator AIBN required for the synthesis of the polymer phase A was added to the o / w miniemulsion at 45 ° C. only after the ultrasound treatment.

 There were obtained 71.9 g of a colorless solid.

 particle analysis

The particle analysis was carried out by means of DSC analogous to Example 1. For the evaluation, heating curve 2 was used. A 1st order phase transition is found. Heating curve 2: onset temperature = 46.5 ° C, peak temperature = 52.8 ° C, delta H = 47.5 J / g. Example 3 - Preparation of the Polvmer Particles According to the Invention

starting materials

 Table 5: Monomer phase A for the construction of the polymer phase A.

Substance Mass [g] Percentage [weight / ο] ¹ monomer ²

 ODA 27.00 45.0 I

 HDA 27.00 45.0 I

 ALMA 2,40 4,0 III

 BzMA 1.20 2.0 IV

 HPA 2.40 4.0V

 1: Relative to monomer phase A.

2: According to the classification of the invention.

 For the radical polymerization of the monomer phase A, 0.60 g of LPO was used as the oil-soluble polymerization initiator.

The associated aqueous phase A is composed of 0.30 g SDS, 0.075 g NaHC0 ₃ and 140 g ultrapure water.

Table 6: Monomer Phase B for Construction of Polymer Phase B.

Substance Mass [g] Percentage [weight / ο] ¹ monomer ²

 MMA 19,20 96 VI

 EA 0 S0 4 VI

 1: Relative to monomer phase B.

 2: According to the classification of the invention.

The associated aqueous phase B is composed of 0.020 g SDS, 0.010 g NaHC0 ₃ , 0.020 g NaPDS and 20 g ultrapure water.

execution

 The procedure was carried out analogously to Example 1 with the following changes:

 Both monomers I were completely melted together in a circulating air drying cabinet at 60 ° C.

 After polymerization, the particle dispersion was coagulated by freezing. For this purpose, the particle dispersion was stored for 24 hours in a freezer at -18 ° C. After thawing, the coagulum was filtered analogously to Example 1, washed and dried.

 There was obtained 75.2 g of a colorless solid.

 particle analysis

The particle analysis was carried out by means of DSC analogous to Example 1. For the evaluation, heating curve 2 was used. A 1st order phase transition is found. Heating curve 2: onset temperature = 30.9 ° C, peak temperature = 37.3 ° C, delta H = 48.7 J / g. Example 4 - Preparation of the Polvmer Particles According to the Invention

starting materials

 Table 7: Monomer phase A for the construction of the polymer phase A.

Substance Mass [g] Percentage [weight / ο] ¹ monomer ²

 DCA 54.00 90.0 I

 ALMA 2,40 4,0 III

 HPA 3J30V

 1: Relative to monomer phase A.

2: According to the classification of the invention.

 For the radical polymerization of monomer phase A, 0.60 g of BPO (75%, in water) was used as the oil-soluble polymerization initiator.

The associated aqueous phase A is composed of 0.30 g SDS, 0.075 g NaHC0 ₃ and 140 g ultrapure water.

Table 8: Monomer Phase B for Construction of Polymer Phase B.

Substance Mass [g] Percentage [weight / ο] ¹ monomer ²

 MMA 12,30 82 VI

 Styren 2J0 18 VII

 1: Relative to monomer phase B.

 2: According to the classification of the invention.

 The associated aqueous phase B is composed of 0.015 g SDS, 0.0075 g NaHCOs, 0.015 g NaPDS and 15 g ultrapure water.

The weight ratio of the polymer phases A and B is therefore A / B = 80/20 wt .-% (based on the amounts of monomers used).

 execution

 The procedure was carried out analogously to Example 1 with the following changes:

 Monomer I was completely melted in a convection oven at 80 ° C.

 The aqueous phase A, the monomer phase A and the o / w macroemulsion prepared therefrom were heated at 50.degree. During the sonication, the emulsion was cooled with a water bath (40 ° C). The internal temperature was in the range of 40 to 60 ° C. After sonication, the o / w miniemulsion was transferred to a polymerization vessel preheated to 50 ° C.

 The polymerization initiator BPO required to build up the polymer phase A was added to the o / w miniemulsion at 50 ° C. after the ultrasound treatment.

The o / w macroemulsion of monomer phase B was added dropwise over a period of 35 minutes.

 There were obtained 67.9 g of a colorless solid.

particle analysis

The particle analysis was carried out by means of DSC analogous to Example 1. For the evaluation, heating curve 2 was used. It becomes a 1st order phase transition found . Heating curve 2: onset temperature = 58.8 ° C, peak temperature = 63.7 ° C, delta H = 67.8 J / g.

 Example 5 - Preparation of the polymer particles according to the invention

 starting materials

Table 9: Monomer phase A for the construction of the polymer phase A.

Substance Mass [g] Percentage [wt / ο] ¹ Monomer ²

 DCA 33.00 55.0 I

 ODA 22.20 37.0 I

 ALMA 2,40 4,0 III

 HPA 2 ^ 40 4 ^ 0 V_

 1: Relative to monomer phase A.

 2: According to the classification of the invention.

 For the radical polymerization of the monomer phase A, 0.30 g of AIBN was used as the oil-soluble polymerization initiator.

The associated aqueous phase A is composed of 0.30 g SDS, 0.075 g NaHC0 ₃ and 140 g ultrapure water.

 Table 10: Monomer Phase B for Construction of Polymer Phase B.

Substance Mass [g] Percentage [wt / ο] ¹ Monomer ²

 M MA 19,60 98 VI

 BA (IO 2 VI

 1: Relative to monomer phase B.

 2: According to the classification of the invention.

The associated aqueous phase B is composed of 0.020 g SDS, 0.010 g NaHCOs, 0.020 g NaPDS and 20 g ultrapure water.

 execution

 The procedure was carried out analogously to Example 1 with the following changes:

 Both monomers I were completely melted together in a circulating air drying oven at 80 ° C.

 The aqueous phase A, the monomer phase A and the o / w macroemulsion prepared therefrom were heated at 50.degree. During the sonication, the emulsion was cooled with a water bath (40 ° C). The internal temperature was in the range of 40 to 60 ° C. After sonication, the o / w miniemulsion was transferred to a polymerization vessel preheated to 50 ° C.

 The polymerization initiator AIBN required to build up the polymer phase A was added to the o / w miniemulsion at 50 ° C. after the ultrasound treatment.

There were obtained 76.1 g of a colorless solid.

particle analysis

The particle analysis was carried out by means of DSC analogous to Example 1. For the evaluation, heating curve 2 was used. A 1st order phase transition is found. Heating curve 2: onset temperature = 48.3 ° C, peak temperature = 52.8 ° C, delta H = 57, 1 J / g. Example 6 - Thermotropic PMMA molding compound and molding

 To produce a thermotropic molding composition according to the invention, the polymer particles from Example 1 were melt-mixed at temperatures between 220 and 250 ° C. with an impact-modified PMMA molding compound (LUCITE DIAKON CLH952 and IM 9386 in a ratio of 60:40 by weight). For melt mixing, a 10-zone twin-screw extruder (COPERION ZSK 18) was used. The hot compound strand of the thermotropic PMMA molding compound is intense white cloudy when leaving the extruder die. After cooling to room temperature, it clears clearly visible. The cold compound strand was subsequently granulated.

 The granulated compound was then further processed on an injection molding machine (ENGEL VIKTORY 200/50 Focus) at temperatures of 240 to 260 ° C to solid sheets of dimension 60 x 60 x 2 mm.

 Example 7 - Thermotropic PMMA molding compound and molding

 To produce a thermotropic molding composition according to the invention, polymer particles of identical composition were melt-mixed with the impact-modified PMMA molding composition PLEXIGLAS zk4HC (EVONIK) at temperatures of 210 to 250 ° C. For melt mixing, a twin screw table compounder with co-rotating screw set (COLLIN ZK 25 T, TEACHLINE) was used. After cooling to room temperature, the compound strand was granulated.

 The granulated compound was further processed with a laboratory tabletop press (COLLIN P 200 M) to form a solid plate measuring 50 × 50 × 4 mm. The granules were distributed between two Kapton protective films in the opening of a press frame and then pressed between two chrome-plated and highly polished brass plates at a temperature of 220 ° C and a pressure of 200 bar.

 Example 8 - Thermotropic PMMA solid sheet after the casting process

To produce a cast PMMA solid plate according to the invention (acrylic glass GS) with thermotropic properties, the industrial flat chamber method was used in a simplified version. For the laboratory-scale polymerization, a simple chamber was used, which was formed from two float glass panes (100 × 100 × 5 mm), a 3 mm thick PVC cord as a spacer and four fold-back clamps. The PMMA precursor used was a prepolymer of 10% by weight of the molding composition PLEXIGLAS 7N and 90% by weight of the monomer MMA. A mixture of 15% by weight of the polymer particles according to the invention and 85% by weight of prepolymer was mixed with a magnetic stirrer at high speed for 60 minutes to give a homogeneous particle / prepolymer dispersion. Subsequently, 0.2% by weight (based on the total mass of the particle / prepolymer dispersion) of the polymerization initiator LPO was added with stirring. It was stirred for a further 10 min. The resulting thermally curable particle / prepolymer dispersion was filled into the chamber and heated for 16 hours in a vertical position at 58 ° C in a convection oven for polymerization. The final polymerization was carried out at 110 ° C for 2 hours. Subsequently, the thermotropic PMMA solid sheet was isolated from the chamber. It has a layer thickness of 2.9 mm. Example 9 - Thermotropic PMMA solid sheet after the casting process

The procedure was analogous to Example 8, but was used as a spacer for the chamber, a PVC cord with a diameter of 5 mm. The layer thickness of the thermotropic PMMA solid sheet thus produced is 4.6 mm.

 Optical characterization of Examples 6 to 9

The injection-molded PMMA shaped body (Example 6), the pressed PMMA shaped body (Example 7) and the two cast PMMA solid sheets (Examples 8 and 9) were optically characterized by temperature-dependent measurements of the transmission in the wavelength range of the solar spectrum (280-2500 nm) , FIG. 2 shows both measuring arrangements which were used for optical sample characterization. In both cases, the input beam hits the specimen at right angles. If only the directional radiation component is detected at the 90 ° angle of reflection, this is referred to as normal normal transmission (T _nn ). In contrast, in a normal hemispheric transmission measurement (T _n h), the entire forward scattered (diffuse) radiation is detected in addition to the directional component. The normal hemispheric transmission thus indicates the total transmission of the sample body.

All transmission measurements were carried out with a two-beam spectrophotometer from JASCO (V-670). For normal hemispheric measurements, a 60 mm integrating sphere with a sample holder from JASCO was used.

 The specimens were tempered in a thermostatable sample holder for at least 20 minutes at the respective temperature. The OFF mode was measured at 25 ° C, the ON mode at 85 ° C.

 Taking into account the spectral distribution of visible light (vis) and solar radiation (sol), the integrated transmission percentages Tvis and Tsol were calculated from the measured spectra (according to DIN EN 410: Determination of photometric and radiation physical characteristics of glazing, European Standard EN 410 , German version, European Committee for Standardization, Brussels, 1998).

 An evaluation of the thermotropic switching properties of the samples was made on the basis of the following radiation transmission characteristics: TviSnn, viSnh = percentage normal normal (nn) or normal hemispheric (nh) transmittance in the visible wavelength range (380-780 nm), taking into account the spectral health sensitivity and the normalized relative spectral radiation distribution of standard illuminant D65.

Tsol _nh = Percent normal hemispheric (nh) transmittance in the solar wavelength range (300 - 2500 nm) taking into account the normalized relative spectral distribution of the global radiation.

ÄTabs = Absolute difference of the respective transmittance between OFF and ON mode calculated according to AT _abs = T (OFF) - T (ON).

ΔΤ _Γ6 ι = Relative difference of the respective transmittance between OFF and ON mode calculated according to AT _re i = 100 - [T (ON) / T (OFF) * 100]. AT _re i thus indicates the percentage change in transmission with respect to T (OFF). Table 11: Samples for optical characterization.

Example Method Content ¹ layer thickness

 6 compounding & injection molding 20 wt.% 2.0 mm

 7 compounding & pressing 20 wt% 4.0 mm

 8 casting method 15% by weight 2.9 mm

 9 casting method 15% by weight 4.6 mm

 1: proportion of the polymer particles according to the invention in the total mass of the sample based on the weight fractions used.

 Table 12: Results of normal hemispheric transmission measurements at 25 ° C (OFF) and at 85 ° C (PN).

 Example TVISnh TVISnh ATviSnh ATviSnh TSOlnh TSOlnh ATSOln ATSOlnh

 (OFF) abs rel (OFF) (on) abs rel

6 82% 56% 26% 32% 79% 59% 20% 25%

7 82% 39% 43% 52% 74% 40% 34% 46%

8 89% 60% 29% 33% 85% 64% 21% 25%

9 85% 42% 43% 51% 81% 49% 32% 40%

The specimens of Examples 6 to 9 have a high light transmission in OFF mode (Tvis _nh (OFF) = 82 to 89%). The solar transmission is only slightly lower (Tso (OFF) = 74 to 85%). Increasing the temperature reduces the visible transmission Tvis _nh between 26 and 43% and the solar transmission Tso between 20 and 34%. The relative changes in transmission in OFF mode are between 32 and 52% in the visible and between 25 and 46% in the solar wavelength range.

 FIG. 3 shows the associated spectra of the normal hemispheric transmission using Example 9.

In addition to the measurements of the normal-hemispheric transmission, the pressed PMMA shaped body from Example 7 was characterized by temperature-dependent measurements of the normal-normal transmission. The specimen was heated step by step from 20 to 85 ° C in a thermostatable specimen holder directly in the beam path of the spectrometer. At temperatures of 20, 22.5, 25, 27.5, 30, 32, 34, 36, 38, 40, 42, 50 and 85 ° C transmission spectra in the wavelength range 280 - 2500 nm were recorded. The tempering time was between 15 and 60 min. FIG. 4 plots the transmission values of the normal-normal, visible transmission (Tvis _nn ) against the temperature calculated from the transmission spectra. In the temperature range of the OFF mode (20 to 30 ° C) Tvis _{nn is} almost constant. From a sample temperature of about 30 ° C, the thermotropic circuit starts. In the temperature range of 30 to 40 ° C, the transmission then significantly decreases by more than 75%. Above 40 ° C (ON mode), Tvis _nn decreases only slightly.

This example shows that the greatest decrease in transmission in the region of the phase transition temperature T _{m of} the polymer phase A of the particles according to the invention can be observed. The clouding occurs in a comparatively narrow temperature window parallel to the sample temperature. The switching times are short. Upon cooling, the sample returns to the original transparent state. The clearing takes place slightly delayed at slightly lower temperatures. used abbreviations

 AIBN Azo bis (isobutyronitrile)

 ALMA allyl methacrylate

 BA / 7-butyl acrylate

 BPO dibenzoyl peroxide

 BzMA benzyl methacrylate

 DCA / 7-docosanyl acrylate

 EA ethyl acrylate

 HDA / 7-hexadecyl acrylate

 HEMA 2-hydroxyethyl methacrylate

 HPA hydroxypropyl acrylate (mixture of isomers)

 LPO dilauroyl peroxide

 MMA methylmethacrylate

NaHC0 ₃ sodium

 NaPDS sodium peroxodisulfate

 ODA / 7-octadecyl acrylate

 SDS sodium dodecyl sulfate

 All cited documents are fully incorporated in the disclosure, as far as this disclosure is not inconsistent with the teachings of the invention.

Claims

claims

 Containing polymer particles having an average primary particle diameter between 50 nm and 10 pm based on the total weight

 A. 10 to 100 wt .-% of a polymer phase A, obtainable by free-radical copolymerization of an oil-in-water miniemulsion with a monomer mixture as the oil phase containing

i) from 30 to 99.9% by weight of one or more monoethylenically unsaturated monomers I having at least one C ₂ -C ₄₈ -n-alkyl side chain,

ii) 0 to 60 wt .-% of one or more monoethylenically unsaturated monomers II with at least one Ci Cu-n-alkyl and / or a C ₃ - C ₄₈ - / - alkyl chain side,

 iii) from 0.1 to 20% by weight of one or more monomers III having at least two nonconjugated ethylenic double bonds, iv) from 0 to 69.9% by weight of one or more (hetero) aromatic, monoethylenically unsaturated monomers IV,

 v) 0 to 40% by weight of one or more other, monoethylenically unsaturated monomers V,

and

 B. 0 to 90 wt .-% of a polymer phase B, obtainable by subsequent radical graft copolymerization in the presence of the obtained according to step A) polymer phase A containing a monomer mixture

i) 0 to 100% by weight of one or more monomers VI from the group of the C ₁ -C 10 -alkyl (meth) acrylates,

 ii) 0 to 100% by weight of one or more (hetero) aromatic, monoethylenically unsaturated monomers VII,

 iii) 0 to 50% by weight of one or more other monoethylenically unsaturated monomers VIII,

wherein the weight percent of the monomer mixtures used in the respective stages add up to 100 wt .-%.

 Polymer particles according to Claim 1, characterized in that the polymer particles exhibit a first-order phase transition in the temperature range from -20 to 150 ° C.

Polymer particles according to at least one of claims 1 and 2, characterized in that the monomers are selected from the group I Ia) of the esters of α, β-ethylenically unsaturated C ₃ - C ₄ -carboxylic acids and C ₂ - C ₄₈ - / i- Alkanols, Ib) the mono- and dialkyl esters of α, β-ethylenically unsaturated C ₄ -C ₆ -dicarboxylic acids having at least one Ci ₂ - C ₄₈ -n- Alkylseitenkette as the ester radical and Ic) of the allyl and vinyl esters of Ci ₃ - ₄₉ - / 7- alkanecarboxylic acids.

Polymer particles according to at least one of claims 1 to 3, characterized in that the monomers II are selected from the group IIa) the esters of α, β-ethylenically unsaturated C ₃ - C ₄ carboxylic acids and Ci- Cu-n-alkanols or C ₃ - C ₄₈ - / - alkanols, IIb) the mono- and diesters of α, β-ethylenically unsaturated C ₄ - C ₆ dicarboxylic acids and Ci- Cn-n-alkanols and / or C ₃ - C ₄₈ - / - alkanols and IIc) the allyl and Vinylester of C ₂ - C ₂ - 7-alkane carboxylic acids and C ₄ - C ₄₉ - / - alkanecarboxylic acids.

5. Polymer particles according to at least one of claims 1 to 4, characterized in that the proportion of the polymer phase B in the total weight of the particles is 0% by weight and the monomers III are selected from the group IIIa) of the (meth) acrylic esters of polyhydric alcohols, Illb) the vinyl and allyl ethers of polyhydric alcohols and IIIc) of the bi- or polyallyl allyl, vinyl or (meth) acryl-substituted (hetero) cyclic and (hetero) aromatic compounds.

 6. Polymer particles according to at least one of claims 1 to 4, characterized in that the proportion of the polymer phase B in the total particle mass is more than 0 wt .-% and the monomers III are selected from the group of allyl, methallyl and Crotyl esters of α, β-ethylenically unsaturated carboxylic acids and dicarboxylic acids.

 7. Polymer particles according to at least one of claims 1 to 6, characterized in that the monomers IV are selected from the group IVa) of the vinyl (hetero) aromatic and IVb) of the (hetero) aromatic (meth) acrylates.

 8. Polymer particles according to at least one of claims 1 to 7, characterized in that the monomers V are selected from the group Va) of α, β-ethylenically unsaturated mono- and dicarboxylic acids, Vb) of α, β-ethylenically unsaturated carboxylic anhydrides, Vc ) of the α, β-ethylenically unsaturated carboxylic acid amides and Vd) of the hydroxy, alkoxy, carboxy,

Amino, epoxy, sulfo, silyl and halogen substituted alkyl (meth) acrylates and heterocyclic (meth) acrylates.

 9. Polymer particles according to at least one of claims 1 to 8, characterized in that the monomers VII are selected from the group IVa) of the vinyl (hetero) aromatic and IVb) of the (hetero) aromatic (meth) acrylates.

 10. Polymer particles according to at least one of claims 1 to 9, characterized in that the monomers VIII are selected from the group Va) of α, β-ethylenically unsaturated mono- and dicarboxylic acids, Vb) of α, β-ethylenically unsaturated carboxylic anhydrides, Vc ) of the α, β-ethylenically unsaturated carboxylic acid amides and Vd) of the hydroxy, alkoxy, carboxy, amino, epoxy, sulfo, silyl and halogen substituted alkyl (meth) acrylates and heterocyclic (meth) acrylates.

 11. Polymer particles according to at least one of claims 1 to 10, characterized in that the polymer phase B by copolymerization of 80 to

99.99 wt .-% methyl methacrylate and from 0.01 to 20 wt .-% of a Ci- C ₈ - alkyl acrylate is constructed.

 12. Polymer particles according to at least one of claims 1 to 11, characterized in that the proportion by weight of the polymer phase B in the total particle mass between 5 and 90 wt .-%, preferably between 10 and

50 wt .-%, in particular between 15 and 35 wt .-% is.

13. Polymer particles according to at least one of claims 1 to 12, characterized in that the polymer particles 0 to 10 wt .-% of inorganic particles from the group of silicates or oxides of the elements AI, Si, Zr, Hf, Ti, Zn, Pb and containing their possible mixed oxides.

14. Polymer particles according to at least one of claims 1 to 13, characterized in that the respective polymer phase 0 to 2 wt .-% of a molecular weight regulator selected from the group of Ci Ci ₈ -Alkanthiole contains.

 15. A process for the preparation of the polymer particles according to at least one of claims 1 to 14, wherein the

 A. presents an aqueous phase A of water and surfactant,

 B. 10 to 100 wt .-% of a monomer A containing

i) from 30 to 99.9% by weight of one or more monoethylenically unsaturated monomers I having at least one C ₂ -C ₄₈ -n-alkyl side chain,

ii) 0 to 60% by weight of one or more monoethylenically unsaturated monomers II having at least one C 1 -Cu-n-alkyl and / or one C ₃ -C ₄₈ -alkyl side chain,

 iii) from 0.1 to 20% by weight of one or more monomers III having at least two nonconjugated ethylenic double bonds, iv) from 0 to 69.9% by weight of one or more (hetero) aromatic, monoethylenically unsaturated monomers IV,

 v) 0 to 40% by weight of one or more other, monoethylenically unsaturated monomers V,

 first predispersed with stirring to an o / w macroemulsion, then homogenized to an o / w miniemulsion and finally to a conversion of at least 90 wt .-% based on the total mass of the monomers I, II, III, IV and V polymerized,

 C. 0 to 90 wt .-% of a monomer B containing

i) 0 to 100% by weight of one or more monomers VI from the group of the C ₁ -C 10 -alkyl (meth) acrylates,

 ii) 0 to 100% by weight of one or more (hetero) aromatic, monoethylenically unsaturated monomers VII,

 iii) 0 to 50% by weight of one or more other monoethylenically unsaturated monomers VIII,

admixed, polymerized to a conversion of at least 90 wt .-% based on the total mass of the monomers VI, VII and VIII and the resulting polymer isolated from the aqueous phase, wherein the stated weight percent of the monomer phases A and B to 100 wt. %, characterized in that ultrasound reactors, high-pressure homogenizers, rotor-stator systems, systems with static mixers or combinations thereof are used for the homogenization step to form the o / w miniemulsion containing the monomer phase A and the aqueous phase A.

16. The method according to claim 15, characterized in that the monomer phase B is added under such conditions that the formation of new particles is avoided and the resulting in this polymerization stage polymer phase B as a shell to the resulting in the first polymerization stage of the monomer phase A polymer phase A attaches around.

17. The method according to at least one of claims 15 and 16, characterized in that the monomer phase B is added as o / w macroemulsion in accordance with their consumption.

 18. The method according to at least one of claims 15 to 17, characterized in that for the polymerization of the monomer phase A one or more oil-soluble and / or water-soluble radical polymerization initiators are used.

 19. The method according to at least one of claims 15 to 18, characterized in that for the polymerization of the monomer phase A from 0.1 to 5 wt .-% of radical polymerization initiator based on the polymerizable

Monomer amount can be used.

 20. The method according to at least one of claims 15 to 19, characterized in that one or more water-soluble radical polymerization initiators are used for the polymerization of the monomer phase B. 21. The method according to at least one of claims 15 to 20, characterized in that for the polymerization of the monomer phase B from 0.01 to 1 wt .-% radical polymerization initiator based on the amount of monomer to be polymerized.

 22. The method according to at least one of claims 15 to 21, characterized in that the polymerization temperature for the respective polymerization stage between 20 and 100 ° C, preferably between 50 and 95 ° C, in particular between 60 and 90 ° C.

 23. The method according to at least one of claims 15 to 22, characterized in that anionic and / or nonionic surfactants are used. 24. The method according to at least one of claims 15 to 23, characterized in that the amount of surfactant is chosen so that the critical micelle concentration (cmc) of the surfactant in the aqueous phase of the o-w miniemulsion containing the monomer phase A is not exceeded.

25. The method according to at least one of claims 15 to 24, characterized in that the pH of the aqueous phase A by the addition of buffer substances, such as sodium bicarbonate, for the free radical polymerization is advantageously designed.

 26. The method according to at least one of claims 15 to 25, characterized in that the monomer phase A and the aqueous phase A before the union to a o / w macroemulsion to a temperature between 25 and 100 ° C, preferably between 30 and 60 ° C tempered.

27. The method according to at least one of claims 15 to 26, characterized in that the solids content of the obtained after completion of the polymerization aqueous dispersion 10 to 70 wt .-%, preferably 20 to 60 wt .-%, in particular 30 to 50 parts by weight. % is.

28. The method according to at least one of claims 15 to 27, characterized in that the polymer particles according to at least one of claims 1 to 14 after completion of the polymerization by a sequence of precipitation or coagulation, filtration, washing and drying from the aqueous phase to be won.

29. A method according to any one of claims 15 to 28, characterized in that the polymer particles according to at least one of claims 1 to 14 after completion of the polymerization by addition of salts containing polyvalent cations such as Ca ^2+, Mg ^2+, or Al ^{3 +} , be precipitated or coagulated.

 30. The method according to at least one of claims 15 to 29, characterized in that the polymer particles according to at least one of claims 1 to 14 after completion of the polymerization by freezing at temperatures between 0 to -40 ° C, preferably - 10 to -30 ° C. to be coagulated.

31. The method according to at least one of claims 15 to 30, characterized in that the polymer particles are obtained according to at least one of claims 1 to 14 after completion of the polymerization by coagulation, dewatering and degassing with a screw extruder from the aqueous phase.

32. The method according to at least one of claims 15 to 31, characterized in that the polymer particles are coagulated according to at least one of claims 1 to 14 after completion of the polymerization in only one process step with a screw extruder, dewatered, degassed and mixed with a molding material as matrix plastic ,

33. plastic, characterized in that it is based on its total weight a. 1 to 80% by weight of polymer particles according to at least one of claims 1 to 14,

 b. 20 to 99 wt .-% of a matrix consisting of

 i. 50 to 100 wt .-% of at least one matrix plastic and

 ii. 0 to 50% by weight of further additives, such as, for example, lubricants,

Anti-blocking agents, release agents, dispersants, antistatic agents, flame retardants, colorants, impact modifiers, plasticizers, adhesion promoters, fillers, reinforcing agents, blowing agents and stabilizers, such as antioxidants, light stabilizers, heat protectants,

 contains.

 34. Plastic according to claim 33, characterized in that it is molded into a plastic sheet or foil having a layer thickness of 2 mm in the temperature range from -20 to 150 ° C, a change in the total Lichttransmissi- onsgrads according to DIN EN 410 of at least 5% to the maximum total light transmission of the plastic sheet or foil shows.

35. Plastic according to at least one of claims 33 and 34, characterized in that the matrix plastic used is a thermoplastic molding compound from the group of polyethylene standard homo- and copolymers (eg PE-LD, PE-HD), the ethylene copolymers (PE-ULD, PE-VLD, EVA, EVOH, EBA, EEAK, EMA, EAMA, COC, EIM), polypropylenes (PP), styrenic polymers (PS, ABS, SAN), polyvinyl chlorides (PVC), polyvinyl butyrals (PVB), thermoplastic polyurethanes (TPU), polymethacrylate homo- and Copolymers or Impact Modifications (PMMA, AMMA, MBS, MABS, PMMI, PMMA-HI), the polyamides (PA), the polycarbonates (PC) and PC blends, the polyester of terephthalic acid (PET, PBT) and blends, polyaryl sulfones (PSU), polyether sulfones (PES) and cellulose derivatives (CA, CAB, CAP).

 36. Plastic according to claim 33, characterized in that a thermoplastic molding compound from the

Group: polymethyl methacrylate (PMMA), impact-modified variants of PMMA (PMMA-HI), methyl methacrylate copolymers (AMMA),

Polymethacrylmethylimide (PMMI), transparent polyamides (PA) based on aromatic dicarboxylic acids or branched aliphatic or acyclic diamines, transparent polyamides (PA) based on dodecanedioic acid and a cycloaliphatic diamine, polycarbonate (PC) based on bisphenol A, polyethylene terephthalate (PET) , Polystyrene (PS), polyvinyl butyral (PVB) and thermoplastic polyurethane (TPU) is used.

 37. Plastic according to at least one of claims 33 and 34, characterized in that as precursor for the matrix plastic curable molding materials and curable casting or laminating resins, such as transparent or translucent formaldehyde resins, unsaturated polyester resins, epoxy resins, Silicone resins, diallyl phthalate resins and diallyl diglycol carbonate.

38. Plastic according to at least one of claims 33 and 34, characterized in that thermally curable prepolymer mixtures of polymethyl methacrylate (PMMA), methyl methacrylate (MMA), at least one radical polymerization initiator and optionally (crosslinking) comonomers are used as precursor for the matrix plastic ,

39. A process for producing the plastic according to at least one of claims 33 to 36, characterized in that the polymer particles according to at least one of claims 1 to 14 are mixed with the matrix by compounding, in particular in an extruder or kneader.

40. The method according to claim 39, characterized in that the plastic according to at least one of claims 33 to 36 then by suitable methods, such as extrusion, calendering, extrusion blow molding, injection molding, injection compression molding, injection molding and pressing, in shaped bodies such as solid sheets , Web plates, corrugated sheets, films, rods, tubes or other shaped body is formed.

 41. The method according to at least one of claims 39 and 40, characterized in that the plastic according to at least one of claims 33 to 36 subsequently with other materials, such as glass, plastic, wood, metal and the like, for example by coextrusion, multi-component injection molding, Bonding, laminating, pouring, spraying, knife coating, flooding and the like.

42. A process for the production of the plastic according to at least one of claims 33, 34, 37 and 38, characterized in that the polymer particles according to at least one of claims 1 to 14 mixed with the curable precursor of the matrix plastic and hardened into plastic parts, such as plates, films and the like, or to composite materials, such as laminated glasses.

43. Use of the plastic according to at least one of claims 33 to 38 for the production of moldings and plastic parts, such as solid plates, web plates, Well plates, films, rods, tubes and the like.

 44. Use according to claim 43 for glazing of buildings, vehicles, conservatories, greenhouses and greenhouses; for glass facades, glass façade elements and curtain walls; for solar control glass and light directing solar control glass; for insulating glass, heat-insulating glass and insulating panels; for laminated glass, safety and sound insulation composite glass; for carports, balcony glazings, patio roofs, glasshouses, pool hall glazings and roofs; for roof, overhead and skylight glazing; for industrial glazing; for lighting components, skylights, rooflights and barrel vaults; for profiled glass, hollow panes and panels; for transparent insulation; as covers for solar collectors and photovoltaic modules; for sunscreen films and varnishes; for agricultural and greenhouse films; as a laminating film for example laminated glass; for interior glazing, partition walls, room dividers, shower cubicles, glass doors and sliding glass doors; for decorative glass; for luminaire covers, lampshades, reflectors and light guides; for optical lenses and spectacle lenses or their coatings; for illuminated advertising and neon signs; for traffic and information signs and for packaging.

45. Particles obtainable by copolymerization of

 a. From 30 to 95% by weight of one or more vinyl monomers having an alkyl side chain with at least 12 C atoms,

 b. 0.1 to 10% by weight of one or more crosslinkers,

 c. From 3 to 70% by weight of one or more vinyl monomers having from 1 to 11 carbon atoms in an aliphatic side chain optionally comprising one or more functional groups,

 d. 0 to 50 wt .-% of one or more vinyl monomers having an aromatic side group, which is optionally substituted.

Particles according to claim 45, characterized in that in addition a further layer is grafted on, wherein the layer is obtainable by polymerization of one or more vinyl monomers having 1 to 11 carbon atoms in an aliphatic and / or aromatic side chain.

 Particles as claimed in claim 45 or 46, characterized in that the particle exhibits a first-order phase transition in the temperature range from -20 to 150 ° C.

 Particles according to one of claims 45 to 47, characterized in that the vinyl monomers are selected from acrylates, methacrylates, acrylamides, vinyl ethers, vinyl esters and mixtures thereof.

Particles according to one of claims 45 to 48, characterized in that the mean particle diameter (d50) is 100 to 2000 nm, preferably 100 to 500 nm.

50. Particles according to at least one of claims 45 to 49, characterized in that the particle diameter d90 value is at most 200% greater than the d50 value.

 51. The particle according to claim 45, characterized in that the particle contains from 0 to 10% by weight of inorganic particles from the

Group of silicates or oxides of the elements AI, Si, Zr, Hf, Ti, Zn, Pb and their possible mixed oxides.

 52. A molding composition containing a matrix and 1 to 50 wt .-% of particles according to any one of claims 45 to 51 and / or

 Particles obtainable by polymerization

 a. 30 to 99.9% by weight of one or more vinyl monomers having an alkyl side chain with at least 12 C atoms,

 b. 0.1 to 10% by weight of one or more crosslinkers,

 c. 0 to 70 wt .-% of one or more vinyl monomers having 1 to 11 carbon atoms in an aliphatic side chain, which optionally comprises one or more functional groups,

 d. 0 to 50 wt .-% of one or more vinyl monomers having an aromatic side group, which is optionally substituted.

53. Molding composition according to claim 52, characterized in that the matrix is transparent.

 54. Molding composition according to claim 52 or 53, characterized in that takes place in the temperature range from -20 to 150 ° C, a change in the normal hemispheric transmission in the solar spectral range of the molding composition of at least 5%.

55. Molding composition according to one of claims 52 to 54, characterized in that the matrix is selected from (meth) acrylates, polycarbonates, polyethylene terephthalates, polyamides, polyolefins, polystyrenes.

 56. A process for the preparation of the molding composition according to one of claims 52 to 55, characterized in that particles according to one of claims 45 to 51 are compounded with a matrix.

 57. Moldings obtainable by molding the molding composition according to one of claims 52 to 55.

 58. Shaped body according to claim 57, characterized in that the shaped body is a solid plate, a web plate, a corrugated plate, a foil or a tube.

 59. Use of the moldings according to claim 57 or 58 as overheating and glare protection in conservatories, greenhouses, carports or for building glazing.